It's totally normal to worry! Even though you know everything will be fine and he'll have a wonderful experience, you can't help but worry.
My oldest child is 24 and I still worry about her. Now that she has a baby, I worry about the baby. I don't go into full-on panic mode, but a mom worries.
When my kids were young and had to be away from me, I always hid a little note in their backpacks or suitcases for them to find once they got where they were going. After a while, they were used to it and that was usually the first thing they'd look for.
My son saved his. We even had one of them hanging by the front door.
I did an outline of my hand and inside it I wrote, "No matter how far away you go, my love is always with you. ~ Mommy"
You'll miss your son like crazy, for sure. Say a prayer that he'll be safe and know that he'll be so happy to get back home to you.
Hang in there, Mom. Try not to worry TOO much.
Best wishes.