Regarding power issues, I find that with ASA 400 film, power output, even when bounced, is sufficient, as long as the ceiling is not too high, like in a church, for example.
With bounce flash, you would probably be photographing subjects that are about 1-3 metres away from you anyway. Any further and the flash becomes a point source of light. It not only makes the lighting look artificial (if you have enough power to bridge the distance), and it does need greater power output or a higher film speed.
With a small unit, you could use it as a direct source of light from the side instead, if you choose to use low speed film. I believe there's a thread here somewhere describing how to go about it.
Clarence