The age group for this toy would be for children ten and up.  Parent supervision would be recommended.  (We would not want this thing to be pointing at anything after launch.)  By playing with this toy, children could learn about chemical reactions and "rocket science."  By mixing the two components, the kids can observe the reaction and its affect as they expand and send the rocket flying or racing away.  They could also try different proportions of the two components to attempt a better reaction.

The materials that this rocket would be made of would ideally be soft and durable.  Soft so that it would cause minimal damage should it hit something, and durable so that it would not break after enduring the reaction.  It that is not possible, at the least the tip should be made of soft material.  It should also be machine washable, or at least easy to clean.  The structure is simple enough, so it should not cost too much to make.