Finishing hardwood floors with shellac - bad idea?
I can think of two good reasons not to use shellac.


It is not as durable as polyurethane.
Lap marks show (sometimes a lot). It not easy to get a smooth finish, especially because it dries quickly.


Because you do not want to deal with the fumes of oil based polyurethane, I'd recommend using water based polyurethane. (It is only the oil based that has the real nasty fumes.)

You get much better durability, (not as good as the oil based) it is pretty easy to apply, and it dries quickly (not as fast as shellac).

It is kind of the best of both worlds. It has some of the strength of oil, and the low fumes like shellac.