i know folks that have gone on rick steve's tours and enjoyed them.
that said, if you are under the age of 50, do it yourself. if you are afraid of tackling it by yourself, i suggest reading rick steve's books. 'europe through the backdoor' is a good one for those just starting out. my wife and i are in our late 20's (no kids) and we are about to take our fourth european vacation together.
i love the rick steves books for frank recommendations on things to see and avoid. on our last trip, to spain, we had a seamless experience. it really is doable, and for cheaper than a tour would be.
his website has a message board that is a good resource as well.
i would also caution you to not try to cram as much as possible into one trip. the national lampoon "european vacation" model is not the one to follow. as much as you may think that this may be your only time to go to europe, if you have fun, you WILL be back. therefore, travel like you'll be coming back. i'd suggest no less than 2 nights at any one place. you don't want half of your trip to be spent on a train and walking to and from the station to your hotel room.