Pass the Parcel, Pin the Tail on the ..., also games like "stand on the red/blue/whatever spot when the music stops" are a hoot at that age
I found a "hunt the... finger of fudge, I did" worked well
only invite as many people that will fit in the house incase it rains - three or 4 will be fine
Food - just do sarnies, crisps, fruit, cakes - they won't want too much anyway
don't bother, unless you want to, with party bags
how about table cloth / some blankets - I got an enormous disposable white table cloth from Asda's party section to sit them all on - scooped it up and recycled it when done
errr, not sure what else - that covers food, drink (squash), cake, games... what else could you need?