My son is starting his senior year.  I am finding myself feeling so emotional about it. 
You must be having bitter ,sweet emotion.I remember my mom was also emotional when i left boarding school for the first time.
Yes, I have this feeling of excitement for his new adventure, but also worry. And I'm just going to miss him so much, he's a wonderful kid.
But you can make arrangements such that you see him every weekend.
I don't know that he'll appreciate that! Mostly I think I'll look at his childhood pictures for a while and have a good cry.