I did DIY at home parties at that age. Proper 1970s ones like i had as a child. 9 other boys invited, so 10 altogether with my DS. Proper Birthday Tea squashed around the table, (sandwiches, mini pizza, crisps, jugs of squash, mini babybels, mini peperamis, cucumber, peppers, midget gems etc). Birthday Cake in the dark, singing and blowing candles. Got themed paper napkins, plates, table cloth, cups etc off the internet, very cheap.
Then DH and I did musical statues, pin the tail on the donkey (or similar) and pass the parcel. Followed by letting them all play with the HUGE amount of lego we had. Then they all got collected after about 2 hours.
Children had a whale of a time, didn't have to invite the whole class, party bag cost was minimal and after that LOADS of the other mums did the same kind of party.
The reason i did it was that my DS as a little boy HATED crowds and loud music/discos and would cry if we went to a party like that.