I agree with what others have said. There are ways to go on trips without spending a fortune. I do it every summer with my three kids due to living so far from family thanks to the military. We aren't rich by any stretch of the imagination but I make it work and I save a little bit every month for it. We travel with a cooler in the back of the mini van with grocery store bought food for meals, some that I purchase slowly starting a few months before the trip ( box cereal, snacks, drink boxes etc). Since I travel alone with three smaller children I don't camp in a tent but we drive long distances each day and have minimal hotel stays.
I have to disagree that spending family time on a vacation like Disney is frivoulous however! Family time does not always have to be 100% educational. Kids, smart or not, are still kids and fun is good! Some people will always have more than others, thats just life and you can't worry about what other parents are providing...its not worth it!
I don't know how far said museum is from you guys, but it is doable if you really think outside the "man its expensive, we'll never be able to do it and no one is available to help" box. It may not be a trip you can take tomorrow, but it doesn't have to be 10 years from now with a little inventiveness.
