If I was going to try and do this on the cheap, I'd do the following:
Hydrogen Peroxide decomposition monopropellent motors - Easy and cheap to build, no flaming explosions at failures (or at least, lower likelihood) and no flammable vapors. Pressurized for simplicity (no pumps) w/ a regulator for fuel flow, using something cheap like nitrogen. It's cheaper and easier to work with than exotics, and for the specific challenge should be more than good enough.
Instead of spending a lot of time trying to perfect a finicky throttle-able engine, I'd have a single big sustainer that can _almost_ lift the craft, and then a bunch of simple tiny H2O2 thrusters around the edge that both give it the extra thrust to take off (and descend, if all engines are off, the sustainer would give it a slow descent) and stabilize. The weight of H2O2 expended during the flight would need to be taken into consideration too, of course, the lander should have 'negative bouyancy' when at near empty.
To reduce dependence on gyroscopes and complicated stability systems (Armadillo has lost a few to computer and gyro mishaps) I'd try and make it dynamically stable. The lower the center of gravity, the better, maybe suspending the sustainer above a hollow center 'donut' would work, for instance. Something like this would make the lander neutrally stable, so you can reduce the complexity of the guidance task.
