I had a last minute "throw it together" party at that age (Local cookery centre left me down on "Pizza and Cupcake making" party literally at 5pm on Friday for a Saturday morning event).
I bought pizza bases and sauce and grated cheese and various toppings (put out in bowls) and got them to make their own pizzas. Then I baked these (and cleared and reset the table) while they played a few games outdoors.
Sandwiches - if you have large cutters, make ham sambos with stars shapes and jam ones with gingerbread men shapes (or whatever shapes you have) - they enjoy the novelty and not having crusts.
One packet of chicken goujons thrown in the oven with the pizzas, and split between the 2 ends of the table.
Couple of bowls of crisps laid along the table.
Couple of bowls of cherry tomatoes and some red pepper sticks (I was surprised just how popular those latter 2 were!!).
I ended up clearing the table off (again) and laying out 3 cupcakes each, a few bowls of different coloured butter cream icing, some sprinkles and chocolate buttons etc, and letting them decorate their cupcakes to bring home (no time to let them bake these - which had been the plan for the cookery school). Some ate theirs, some brought them home (have paper plates and a 2nd one to cover the top, or else some paper/sandwich bags).
Less messy desserty things would be bowls of berries and chopped fruit, already decorated buns or brownies or slices of cake, maybe a few jellies.
Basically, all finger foods (no need for cutlery).
Jugs of squash or plain water are absolutely fine.
PLastic/paper tablecloths, paper napkins, paper plates and paper cups are all your friends for this. Themed is nice, but even just matching or contrasting colours is fine. Get enough to be able to replace a few, and I tend to even use paper plates/bowls for serving things in the middle.
If you HAVE them or would be likely to make lots of use of them, buying plastic plates and bowls and glasses (either small DC types, or camping/outdoor use types) would be somewhat better for the environment, but try to get types that can go in the dishwasher (if you have one) and you may need to wash up as you are going along if you don't have spares.
Have a bin bag in your hand to clear the table and scoop everything into it. (Or all wasted food, napkins and tablecloth - throwing the reusable plates etc into the (emptied in advance) dishwasher). One of the emptiest squash jugs becomes the "bin" to empty the dregs from glasses into before either black bag or dishwasher for those, and the jug is then easy to tip down the sink.
Wave all guests goodbye. Hit "on" switch on dishwasher. Pour cold glass of wine and let party DC open their presents while you get to relax.