Our first friend party was age 5.
Park, with toilets and a covered BBQ area ( I had to get up obnoxiously early to snaffle it) and morning tea, which was fruit kebabs, homemade sausage rolls, homemade tiny pizzas, and lego man cupcakes. And a water bottle for each child which I had removed the label off and made their names laminated and stuck on.

Some wise BB last once told me the kids get to invite as many people as their age. I guess you will be going way over that!