Keep younger siblings out from underfoot: Do your best to distract younger children when an older sibling has a friend over (better yet, pair a younger child with his own playmate). Much as you may welcome a playdate as easy entertainment for both of your kids, being saddled with a little brother or sister isn't fair to the child having the playdate — not to mention frustrating and possibly even unsafe for the younger one, who can't keep up with the older kids' more advanced (and daring) play
Let the kids choose what to do: Plan two or three activities you think the children may enjoy, suggests Lisa Church, but don't insist on trotting them out if the kids are doing fine on their own. This will only agitate a child who feels that you're intruding on special playtime with his friend. Instead, wait for your cue — usually something along the lines of, "We're bored. What can we do?"
Be prepared for "break time:" Besides having some healthy snacks on hand, it's a good idea to have a quiet-time activity ready in case the kids get too wound up — or are beginning to butt heads.