21st birthday

My boyfriends 21st birthday is in July, and his best friend is going to come visit to surprise him, and neither of us are 21, so we cant get alcohol.. but I want to have some kind of little party for him, I was thinking a surprise party with a bunch of his friends, but I have no way of telling them about it, and plus I dont think my mom would go for that.. so I guess it will just be me, him, and his one friend who is coming to surprise him..
but, what are some ideas for a little party for a 21 year old, without alcohol, and not too expensive.

why cant you get alchahol?
just because the legal age is 21 doesn't mean you cant get somone else to buy it for you

no one around here likes to buy alcohol for other people

No alcohol therer are plenty of special things you can do for him that don't involve alcohol plus you're probably right your mom wouldn't go for that so just do something nice so you can show your mom she can trust you!