Good idea or bad idea?

When you say “our class”, do you mean your child’s school classroom? If you hand invites out in the classroom you have to invite everyone. Everyone also isn’t going to come either but imagine being that one kid that’s left out. That can’t be good for their self esteem.

Just invite the kids your kid actually interacts with

I'd probably say you'll have 5 that won't come and maybe 2/3 that will say yes then drop out, could you ask if they'd host 22/3?

I wouldn’t do a venue then. I would take cupcakes to the school and then allow him to invite his actual friends to the party. Text or email the parents that your child is actually connected to. 30 kids sounds like a huge class. In most schools, you have to send an invitation to everyone in the class so unless you’re prepared to have it at your house, I would take that option off the table completely.