Inviting specific kids only to birthday party - help

[Bountychocolate]

How do I do this? My son is going to have a small gathering at home to celebrate his birthday this year. I can't afford a big party etc, and feel I can organise something nice at home. However our home can't accommodate the whole class. I've told him he can invite 8-10 friends.

Problem is he's chosen a few friends in different year groups and I don't have the parents contact details. How do I handle this?

Is it ok to send him to school with a select number of invites to hand to invitees? I'd rather save hurt feelings and contact the parents directly, but I'm stuck as obviously don't have phone numbers...

What's the etiquette in this situation?

How old are they all? Do you know which classes the others are in? Could you ask nicely if the class teacher would quietly put an invite into the relevant book bags? Or would you recognise their parents or be able to work out how they are in the playground to hand over yourself?

He's 7, and I've tried figuring out parents over the past few days but to no avail.

Maybe asking the school to distribute is the only option?