pastry whirls are good - puff pastry rolled out, spread with jam, rolled up and cut into wheels - turn on their side and bake in the oven on baking paper until golden - leave until cool and peel off the paper.
We always did cones at partys - make your own cones and then lay out bowls with different toppings for them o dip their cone into - like chocolate strands, cocoa powder, rainbow drops - always goes down well.
I agree with spud queen, you can't beat the old favourites where little ones are concerned.
You can also put out carrot sticks, baby tomatoes, grapes, raisins etc.
I wouldn't do too much, most of it will end up mashed into the carpet or floor anyway.
What I did a couple of times, was to get little boxes - kind of like the ones you get at mcdonalds, and put a picnic selection in them - carton of drink, raisins, sandwich, sausage rolls, crisps and a cake - then just had extra if anyone wanted them - it saved making too much. - It also meant that they all went into the garden to eat it and there was no mess in the house and I didn't need to try and sit them round the table.