How about a wash station? Either some wipes or a bucket of warm water and a towel?
Have you got enough serving utensils and cutlery?
I second the juice - we bought little water bottles (like the macca's ones) and juice for the kids at DD's party. Because it was summer (and a 40 degree day!) and we had a bouncy castle, we figured 3 per child... and only had a couple left!
Have you got enough seats? Some for the adults and maybe a cushion or rug area for the kids?
Matches for the candles? (You'd be surprised how many people forget that!)

Did you check the cook times and temps for the oven food? Perhaps have a look at it and work out what can go in when. We had different foods needing to be cooked for different times on different temps. So we cooked the longest stuff on the highest temp first and then reduced oven temp - takes less time to cool than heat up.

Have you got helpers? Just to help you get food out and still keep an eye on the kids. We worked it so that DH did all the food prep upstairs whilst I was down entertaining the kids and Mum's.


There is one more thing you forgot... my invite!