Guess you need about same stuff as in Formula 1 races:
-Earplugs are must. Take few extra pairs 'cause you'll see some parents bringing their kids to race without them
-Good hat, maybe a towel to cover your and kids neck.
-Plenty of pure water (coke just makes you more thirsty)
-little suntan lotion for kids and you.
It's amazing how fast you can burn your skin in those races. If it's hot you don't need to find a toilet; You're going to sweat like a eskimo in a hot place.
Have fun, do not make too tight schedule and buy some souvenirs.
I bought a McLaren-Mercedes wrist-watch from Hungarian F-1 GP. Nice chronometer made of steel and carbon-fibre. Not cheap but propably lasts my whole life
