Without a doubt, my favorite place to travel with kids is Walt Disney World. It's family friendly and there's such a great diversity of rides, shows and activities. There's no way you or your children can get bored there.
I took my girls there when they were 8 & 4, respectively. They really had a great time (and I did too). Now they're 15 & 11, and we're getting ready to go to Disney World again in a few weeks. I think they're more excited to go there now (than they were when they were younger).