How about half-half ? Inviting the classmates is good as your daughter is happier and it is a good chance to meet her classmates' parents. I think you don't need to invites all kids in the class, just ask your daughter to name some of her best friends.
請同學會玩得開心d,agree
but u can invite your friend's children,yoo.
you need not worry too much,when playing game,they will play together,more children,more fun.
I will usually invite all including classmates, relatives and my friend's kids as they will meet each other regularly. Of course, you have to consider the venue capacity and $$$.