Rate attractions on the D.C. area.?

I asked this question last week, but Yahoo wasn't letting me add details, so the answers were off-base and I didn't want to waste everybody's time.

I am planning a vacation in the D.C. area this summer. I am focusing on zoos, science museums and amusement parks within a two hour drive of D.C.

I have checked AAA, on-line, etc. What I'm looking for here are reviews - which zoos, science museums etc are great, which ones are a waste of time/money, and so on. I have a week, and I like to devote each day to one destination, so I want the seven best things to do! I am also open to recommendations for those little-known but really great attractions that only the locals know about.

P.S. I will be staying north of DC. I am also seeking recommendations on where to stay. What is within reach of the Metro (which I've been told is the easiest way to get in/out of DC)? I would prefer a city with some inexpensive, family-friendly theater, like colleges, community theater, etc. That's a good way to spend an evening. I'd like the tickets to be less than $20 per adult. Again, I'm also looking for little-known, family-friendly ways to spend an evening.