Few thoughts:
I had no problems watching my son at the airport leaving for USAFA. Maybe a bit misty-eyed, but no big deal. The clincher didn't come until I got home after work that evening and walked into his room and realized he WASN'T COMING HOME!!!
For real!! When I spoke to him that evening (he spent the night with a friend before I Day), I really lost it. Couldn't talk because I was crying too hard. THAT was the hard part. The next morning when I spoke to him for 30 seconds on his way in, I held it together for his sake. Luckily we have Webguy for USAFA and I was able to find a lot of pictures of him that day going through the inprocessing. And realized at that point I no longer felt sad, or upset, but... in looking at all the pics... more JEALOUS of all he had to look forward to!
As far as all the opportunities they'll have, my son was in Drum and Bugle and got to spend a day in NYC (where he had countless people thank him for his service, pay for his meals, tickets, allow him to go to the heads of lines, etc.), a weekend in Las Vegas (where he managed to see 4 shows in one day!), play (trumpet) on the field during halftime in a bowl game, and a LOT of other travel opportunities. He's excited about the upcoming summer and recently posted as his Facebook status, "Parachute school this summer! That's right, my college rocks!"
Finally, regarding the cards - from what I understand that's okay for Navy and WP, but it wasn't - at least for first detail for my son - at USAFA. They were strongly encouraged to only have "business sized, plain white envelopes with nothing to make them stand out". My husband included a picture in one early in the game and son defintely let us know NEVER to do that again. By second detail they cared less and usually allowed them to read their mail on their own out at Jacks, but seemed like the first few weeks they read them standing at attention in the mailroom while the cadre walked around and read/confiscated/made fun of anything that was even slightly non-uniform (or had the whole group do pushups, etc. to "pay" for it)! I had stocked up on a zillion cards to send him and ended up with a lot left over. I still use them occasionally just so he has some (non-bill) mail in his mailbox but seems kind of unnecessary sending him "hang in there, you can do it, things will improve" cards when he's all "Life is great!"