What's the party invite rule for children?

[Mrsknackered]

DS turning 5 in a few weeks. He's asked for a party instead of presents (we wouldn't be able to afford to do both really)
My mum and stepfather have kindly offered to pay half for him to have an 'explorer party' which consists of food, 'exploring', animals and dancing. Parents can stay if they like, but don't have too. Like I said before, we couldn't pay for this party alone.
Only issue is there's a maximum of 12 children. There's 25ish in his class/year. His list was easy for him to write, but it consists of 8 boys and 4 girls. Is this really out of order on the other children?
He's been invited to two parties, one was all boys and the other he couldn't attend so I'm not sure how they delegated invites.
Help! I get anxiety about this kind of thing! Cancel and change party or AIBU stick with the 12?

Absolutely fine, enjoy!

There are no 'rules'.

You do what suits your family and budget.

Do what suits. Since when are there rules about who to invite to a 5 year olds party?

No rules as such but it would be unkind to leave out 1 child or one boy for eg. Sounds like your list is fine unless it's a very girl heavy class and he's invited all but 1 boy or something.

Whole group or half here too plus I make mine return invites for any that they have accepted as I feel it's rude to accept hospitality and not return it.

It would be ridiculous if every kid had a class party - 30 in a year! Just invite who you want and let others do the same.