We visited Discovery Place on the Monday after Easter. We were there very close to opening time since we weren't sure if it would get crowded with Spring Breakers. We had the second floor mostly to ourselves for a good 25 minutes or so. We got to see and try a lot of things that probably had waits later on. The museum is really nicely laid out and decorated with kids in mind. Bathrooms seemed plentiful and well placed.
Our 6 year old had a good time running around trying the different exhibits. I'm not sure he "learned" a lot, but he liked the hand on-ness of it. The 2 year old just wanted to see what her brother was doing. For mom and dad it was a fun morning, but not ecstacy. We considered the IMAX, but with the 2 year old we decided, with the advice of the lady at the admission desk, that it would be a bit much. We did see The Little Prince in the smaller 3D theater and that was quite enough 3D for us. We didn't spend any time in the hands on room for the little kids. By the time we got there it was pretty crowded and a little bonkers. Might have been a better place to start. We had planned on being there long enough to have lunch in the cafe, but we were pretty much done by about 11:30, so we moved on to find lunch elsewhere. We did tour through the gift/souvenir shop. Most of the stuff was pretty overpriced (as expected), but there were a few things to be had for a couple bucks for the kids to take something home.
Overall, I'm glad we went, but I doubt we'd go again on a future Charlotte visit. Unless we just did the IMAX when the kids are older.