Outdoor Pest Control - Wasps & Yellow Jackets - Any idea on how to deter them?

Every summer we get a fare share of wasps and yellow jackets in our back yard. There are several large pine trees behind our back fence. The wasps and yellow jackets build their nests under our overhang, in our patio table umbrella, under our clay shingles on our house, and any where else they can find. We try to foam spray the nests as they are building them but sometimes we can't find them all and keep up with them. Anyone have any suggestions on how we can maybe deter them away from our area or any traps that would work?

My kids are afraid to go out in the backyard during the summer because of these insects.

A guide to wasp and bee control: http://www.extension.umn.edu/distribution/horticulture/DG3732.html