Rocketry is a good activity for Cubs and Scouts. Never got around to running with our Cubs or Scouts, but did do it with our Venturers.
Estes has educators packs of both kits and engines that make the activity more cost effective. Quest also has bulk packs of rocket kits and rocket boosted gliders.
Venturer Model Rockets: Building, Building, Finishing, Finishing, Launching
Venturer Chip Cup Rockets: Build & Launch, Build & Launch