I actually got the idea for this from talking to the others in the Aragorn & Arwen Club, so this is dedicated to them. Thanks so much, guys!
And honestly, if there's anything wrong with this story, I mean no disrespect to Mr. Tolkien or his characters. This idea just wouldn't leave me alone until I got it out on paper - I'm still not sure if I like it or not. Anyway, enjoy! 
This Was My Choice (Arwen's POV)
It was a warm day, as spring in Gondor tended to be. I could hear birds singing as I walked through the courtyard holding my infant daughter Miluiel. Just an average day, it would seem to the casual observer - except that it was anything but.
Oh, Ada, how I wish you were here.
My father’s birthday. Ordinarily it would be a day of celebration, but now it was only a day for memories, of bitter and sweet. Elrond Peredhil had long ago sailed across the sea to Valinor, as had mother mother Celebrían, and now I would not see either of them again except in my memories. A single tear dripped down my cheek as I remembered a day many years ago, but which felt as if it had been only yesterday...
-----
“Sister, get up! It’s Ada’s birthday!”
The first thing I saw that morning was a hand waving in my face. “What?” I mumbled, sitting up to face the intruder.
Elladan, one of my brothers, stood in front of me, wearing a grin that stretched the entire length of his face. Though he and his twin Elrohir were more than 100 years older than I, they still had the playful hearts of very young ellans. “Come on! Don’t you want to go sing to Ada?” he asked eagerly.
Though I was younger, I was in some ways wiser than he, and I saw a probable flaw in this idea. “But ‘Dan, Ada might not like being woken up like this.”
“He will,” said my brother earnestly. “It’s his birthday! Everyone likes to be sung to on their birthday.”
“Okay, if you say so.” I decided to make sure to stand at the back during the singing, just in case Ada really wasn’t in the mood for singing and I needed to make a quick exit from the room.
“’Dan, is she up yet?” called Elrohir, poking his head into my room. The two were virtually identical to most who didn’t know them well - usually only Ada, Naneth and I could tell which was which. But everyone in Imladris knew that ‘Ro was slightly more calm and considerate than ‘Dan; I wasn’t surprised that he’d been waiting politely for me rather than waving his hand in my face.
“Don’t worry, ‘Ro, I am,” I said as I swung my legs over the side of the bed and touched my feet to the floor. Fortunately the floor wasn’t cold - some mornings it was.
The three of us crept to our Ada and Naneth’s bedroom, where soft snores let us know that they were both still asleep. ‘Dan and ‘Ro went to stand right beside Ada so he could hear them well, while I stayed near the door as I’d planned. Then in one slightly off-key voice - courtesy of my brothers - we began to sing:
“Aur onnad meren an le, aur onnad meren an le, aur onnad meren mell Ada, aur onnad meren an le!”
Ada, clearly surprised, sat up quickly, as did Naneth. “What in...hîn nîn, what is going on?” he asked.
“Ada, it’s your birthday!” cried ‘Dan excitedly. “Don’t you remember?”
“Oh yes, I seem to recall hearing something about that,” teased Ada, his eyes twinkling with laughter as he hugged the twins. “Hannon le. But perhaps next year you could wait a few more minutes, eh?”
“Don’t worry, we will!” they chorused.
“Arwen, come give Ada a birthday hug,” called Naneth, smiling. “You looked for a moment as if you expected to be chased out of the room.”
“Well...’Dan and ‘Ro had the idea, but I wasn’t sure if Ada would like it,” I explained bashfully.
“Of course I like it!” reassured Ada. I went over and hugged him, whispering “Le melon, Ada” into his ear.
“Le melon, Arwen,” he replied softly.
The rest of the day, Ada ignored all the tasks he had to do and played the whole day away with Naneth, ‘Dan, ‘Ro, and I. Once during a short break in the games I heard him say to Naneth, “Celebrían, I feel more like an ellan than I have in an age!”
For one wonderful day the five of us were completely carefree, just playing together as a family. This was before Gilraen and Aragorn came to Imladris, before my mother was attacked by Orcs, before we three children had any cares in the world...it was pure bliss. I remembered wishing more than anything that that day would last forever.
-----
My reminiscing was interrupted when I heard Miluiel begin to whimper. “Ssh, mell nin, ssh,” I whispered, rubbing her back.
“Is Miluiel all right?” asked Aragorn, appearing suddenly behind me. Most would have started, but I had heard him coming.
“She’s fine, just a bit impatient because her mother was being sentimental for a moment and paying no attention to her,” I said, smiling at him. It was amazing how he could still be so incredibly handsome after all these years of knowing him. “It would be Ada’s birthday today, you know.”
My husband nodded, a serious look coming over his face. “He was a good father to you and the twins - and to me.”
“Yes, he was,” I murmured softly, feeling a lump come to my throat and tears prick at my eyes. Aragorn sensed what I was feeling and wrapped his arms around me, holding me tight.
“Arwen?” he asked after a moment. “Do you ever wish that you had made a different choice? That you had gone to Valinor with your father and grandmother?”
I thought about that: thought about all that I had lost because of my choice. My mother had gone to Valinor before I’d even met Aragorn because of her attack by Orcs. My father and grandmother had left just after I’d married him, and I knew my grandfather Celeborn tired of Arda and would likely follow Galadriel there soon. Because I had married a mortal I would have to watch him tire, fade, and someday leave the world. And since I had also become mortal, the same would happen to me, and I would be eternally separated from half of my family, save in memory.
But then I thought about all I had gained from my choice: a love purer and richer than any I had hoped could ever exist, queenship of a strong and lovely kingdom, and two beautiful children. Would I want to go back and make another choice, were I given the chance? Now more than ever I knew my answer to that question.
Gently leaning out of Aragorn’s embrace so that I could look into his soft grey eyes, I replied, “This was my choice. I wouldn’t change it for all the world.”
He looked pleased and began to reply, but just then there was a loud outburst and two small boys ran through the courtyard, waving small wooden swords and stabbing them at each other.
“Take that, Lord Elboron!”
“And you take that, King Eldarion!”
“Hey, that’s not fair! You can’t try and trip me, no real warrior would do something like that!”
Laughing merrily, I watched our five-year-old son Eldarion and the four-year-old son of Lord Faramir, Elboron, continue their battle. Miluiel giggled and waved her hands as she watched her brother play. “He’s getting to be almost as good in battle as his father,” I remarked.
“Which one?” asked Aragorn, a note of laughter in his voice.
“Both of them,” I answered, leaning over to kiss him on the lips. “But I was actually referring to your son.”
“Perhaps soon he’ll be ready to be knighted?” he asked, chuckling.
“Let’s wait a few more years for that, shall we?”
----
Ada: Father
Naneth: Mother
Aur onnad meren an le: Happy birthday to you
Aur onnad meren mell Ada: Happy birthday dear Daddy/Father
Hîn nîn: my children
Le melon: I love you
Ellan: young male Elf
Mell nin: my dear
(I hope I got all the Elvish translated at least mostly correctly.
)
