I'm just doing research now, gearing up to finally go reef after doing fish-only for quite a while now, but here's my two cents..
If you're just cycling, I'm going to guess (hope) that your LR is sort of like "base" LR. (Not heavily encrusted with life but with a nice coating of slimy goodness..) If that's the case, I would tend to think you'd be ok keeping it in clean buckets for a few hours.
If it IS pretty well encrusted with life, I'm not sure what to tell you, but obviously everything on it is going to be more sensitive to changes.
What about asking your LFS to hold on to it for a few days while you get truely ready for it? (Don't have high expectations with that though...)
Good luck!