When it comes to making your own launcher, it’s hard for me to do much better than the Instructable I put together a few years back.
If on the other hand you are looking to make rockets, fast and furious, check on my video on YouTube is the place to be. There is also another video where I make a high pressure rocket in about 2 minutes.
Hackerspace Charlotte and later Makerspace Charlotte have had a great relationship with Discovery Place. We created several lab events including LED blinkies, RC Hovercraft, Compressed Air Rockets with parachutes, as well as soldering labs, bug bots, feltronics demos and talks among others.