Hello M.,
ask their mom what foods the kids like or if there are any food allergies. in terms of toys... well, that varies so much. but if you have a a couple games like sorry, candyland, dominoes, cards, parchessi.
one game that is really fun for just about any age is hullaballoo from cranium. it's like musical chairs but on little pads that come w/ the game. they have to touch a specific color, then twirl to the other color then hop, etc. etc. even your 14 month old may enjoy playing it w/ you. that's one that you can keep.
plan your meals. tackle dinner first.
1 night pizza
1 night pasta, rice, chicken?
1 night dinner out
plan one outing: will the swimming pools be open by then?
get kid friendly videos
buy a couple of boxes of crayons
have some paper ready
depending when they're coming, see what's going on at the library.
consider getting 1 or 2 babysitters so you guys can go out to dinner or just enjoy some time together without having to worry about the kids.
Good luck and have fun with your friends!
~C.~