Firstly, don’t vent on social media. You will just be publicly humiliating both yourself, but more importantly, your daughter.
Are any of the non-replying children actual friends of your daughter’s as opposed to just random classmates? If so, I would contact their parents individually. The rest, I wouldn’t bother with.
You’ve got two problems here.
Firstly, the invitations went out too long before an event during the summer holidays. At the time of receiving the invitation, people’s plans wouldn’t be fixed, so they couldn’t say yes or no immediately, then as it got closer, it will have slipped their minds.
Secondly, a whole class party won’t be a priority event during the summer holidays when there are lots of other possible entertainments. Your child’s friends will be keen to go, but the children who she has nothing to do with at school won’t be that bothered, if they have other things to do.
My advice is to forget about whole class parties in the summer holidays, and just invite your daughter’s actual friends in future.