From southern California, to way up north in Alaska...
California:
Legoland -- theme park for ages 2 to 12, in Carlsbad -- has a medieval summer fun
Yosemite National Park - stay at a Registered National Landmark hotel, or a "Housekeeping Camp": camping without the hassle of a tent
San Diego with Kids - About's Guide for California for Visitors has many suggestions
San Francisco - Fisherman's Wharf, Golden Gate Park (with kid-friendly Aquarium, Natural History Museum, and Planetarium), the Exploratorium, Children's Zoo...
Monterey- Fisherman's Wharf, Monterey Aquarium; whales, sea lions...
Disneyland: celebrating it's 50th birthday for 18 months, starting May 2005
Universal Studios Hollywood - popular with teens, for its thrill rides
Northwest:
Washington:
Rosario Resort,Orcas Island- historical & unique
Alaska
Alaska Wildland Adventures - Raft the Kenai River, hike in forest, explore Kenai Fjords National Park by boat, learn about native cultures...