To help keep people out of the kitchen set up a drinks and snacks table on the porch. Stock this with coolers full of ice for drinks, also water, tea and coffee. I'm not a fan of Koolaide and such, kids rapidly learn to drink water or tea around our place, but if you are keep pitchers of of it in the same place. This limits the numbers of trips into the kitchen. No normal ice maker will keep up so lay in a generous supply of ice before people get there.

Consider regularly putting a kid on 'drink and snack duty'. Their job is to check on the drinks and snacks and to help make/get out more as needed.

Before any big get together scatter chairs and benches in ones and twos around the property and well away from the house. Setting up areas where two or three people can have a conversation and/or escape the crowd. Make one or two of these just one chair, preferably with a decent view, and out of earshot of the house. Some people, some times, just need some time alone.

If you have a body of water at hand do have fishing poles handy. Check with fish and wildlife. Some don't require licenses for kids under a certain age and I have known rangers to give a family reunion a one-day pass for free if they were informed beforehand.

If the water is of any significance allocate an adult to act as lifeguard. Work this in shifts. Being on lifeguard duty is a fair reason to get away, or get someone away from, the crowd.

Keep several first-aid kits and fire extinguishers, a bucket of sand does less damage and is quite effective on small fires, handy. You never know when kids will get overenthusiastic and do a header down the stairs or when uncle Billy will fall asleep with a lit cigarette in his hand and try to burn the house down.

With kids outside make it a game to apply sunscreen and check for sunburn. If you press lightly with a finger and the exposed skin looks very light when pull away the skin is burned.