Tricky ages and birthdays

[ShimmeryShiny]

My eldest will be 8 soon and he's at the age where he wants to have sleepovers. I said he could maybe have a sleep over for his Birthday but I would only want 3 friends maximum.
He does have a few other friends too but some I prefer more than others.
Trouble is I'm worried about the others getting wind of it and then saying aww can I come or why haven't you invited me. I don't want anybody to get upset.
Any advice please?

Maybe not helpful when it's to celebrate a Birthday but I have a rule of one friend at a time sleeping over.
I've found groups to be too much trouble and a bunch of kids together in my experience has ended in fighting/arguing, one child being left out of the fun etc.
Maybe spread the celebration out over a couple of weeks?
Less likely other kids will get wind of it and kick up a fuss about being left out of an 'event'.