They will eat pizza and ice cream cake and probably everything else that is not nailed down since they are all growing like weeds and never stop moving. They will swim and play basketball and play Manhunt in the yard with flashlights until they collapse, at which point they will all retire to the basement with sleeping bags and pillows and handheld gaming devices. They'll likely be up most of the night, but as long as they are relatively quiet, we don't care.
In the morning, I will make them pancakes with sprinkles and whipped cream. There will be a goodly number of very groggy faces and some SERIOUS bedhead at the kitchen table. After breakfast, parents will come to collect their kids, and I will fumigate the basement (preteen boy hormones...whew!) and try to identify the owners of all the stray games/socks/T-shirts etc I invariably find while doing so.
This is the routine now; Thing One's birthday party of choice. This is the third or fourth year running. He loves it, his friends love it, his friends' parents think we're nuts. And we are, no doubt. But it makes our boy happy and once a year we can live with it. We just invest in earplugs for the rest of the family! Happy belated birthday to our eldest, coming right up.
And speaking of birthdays, wishing a happy "real birthday" to my beloved mother today as well!