Howdy, may have to light (and direct, produce, etc.) a show in the round with low ceilings (10').  Any advice?  I'm planning on using 4 light trees near the "aisles," but I'm worried about blinding my audience or even hitting the right areas.

In ITR there is no right spot as such, as there is with the pro arch staging. You can utalise light bounce more off the deck &/or the cieling, which will assist your colour wash. If it's an Areana ITR your light trees I wouldimagine would be set up at 4 cardinal compass pionts. depending of the logistics of the space. you can use Silk on the gels to defuse the blat hot spot of the bubble, that could be caught in the sight lines.
While it you would attempt to give an even wash, use the shadows as a friend & to the advantage of the production. When setting the action of the luvvies on stage, with a lot more movement is important. Making it seem  more natural to the punters & the warm props, as Topper suggested in your other ITR thread.
This helps your light rig up, rather than lighting those coventional groupings, which actors tend to be drawn into like magnets. While directing be constantly on the move to view from at least the 4 main cardinal sight lines. The back of an actor can be just as, if not more powerful then from front on, allowing the punters to use thier imagination a lot more. Don't have them standing rooted to the spot like stale bottles of milk, get them to be at ease with moving, with or without motivation.
I have used the old 'dance spot' in the 4  pionts of the house, to asist  the performers  to orientate themselves  during the performance, in black  & brown outs or even generaly. Using 4 seperate colours to depict N, S, E & W. these are only 100watt or so outdoor patio par floods. [West  Red [Port - left], North White [Mast Head] East Green [starboard Right] South Blue [Ocean] or what ever colour apeals to you. , East  Green, South Blue. Green - right], Mast head [white - stars] & Ocean . Leaving them on for the whole show above & behind the audiance, either at the centre of the 4 walls or the each of the 4 corners, which helps & the punters don't notice.
Even using ordinary incandecant bubble fittings, covered with colour gels will help everyone.
You will find indirect wash lighting reflecting off even  darker surfices will illumate, just as well as direct lighting. (as Vicki suggests;- photography with useing reflector umbrellas to bounce the flash or wash lighting]
Even bouncing wash of darker surfices will illuminate the stage.
Hope this puts some light on the problem!