I've put together a technical assessment white paper for the FIRST robotics league, proposing an indoor aerial robotics contest for 12-17 year old kids (and coaches). Target price is under $1,000 and safety is of prime importance. This paper lists the possible platforms--microplanes, helis, quadcopters and blimps--and discusses the pros and cons of each. At this point I've tried most of the options, from helicopters to quadrotors to blimps to ultralight planes and I'm leaning towards quadcopters and blimps as the best choice.
Cost, simplicity and safety pushed me towards the blimps, but I'm concerned about having the kids having to build the autopilot from scratch. Check out the draft of my white paper and tell me what you think.