I used to visit this place at least once a year when I was a kid in the Sixties living in the area, and I could persuade my dad to take us. To my delight, many of the things from the old days are still there, the German submarine, the coal mine, and various exhibit pieces (Craig Breedlove's "Spirit of America", setter of land speed records sticks out especially) and a few others. The new exhibits are exciting, and are designed to involve kids and adults alike. Back then, it was free, but of course, now there are fees. I can see where the cost can get pretty steep for a family of four or five. You might want to limit your extra fee activities on the first visit, to see if your kids really like the experience all that much.
I don't have the energy I had 45-50 years ago, and the place is enormous, an adult without boundless enthusiasm might get tired feet. But there's always another exhibit beckoning you to see it, and you find yourself lured by the adventure of it all. I remember the place being better lit back then, there were actually places I had to use the flashlight app from my smartphone to read labels on artifacts from the submarine (thank you to the folks who were inspired enough by their museums to create smartphones!).
One overriding thing still remains the same, this is a place to create the most wonderful thing in the world, a child's dream. I noticed that my guide (A. J.?) for the coal mine tour kept talking to the kids in our group about becoming scientists and engineers, to make things better for the world. I shook his hand at the end of the tour and told him that this museum still does for young people what it did for me.