Depending on the sconces chosen, they could provide sufficient light by themselves.

If you really want can lights (4" or smaller) , take a look at the CREE LR 4 can lights for inspiration. They come with the housing and trim included.

For a purely decorative purpose, you could look at low voltage 2" mr16 cans.

Presumably, the lighting will be for the vanity area and not the shower/ tub section? Or do you intend to have can lighting over the shower/ tub section as well?

An alternative to can lights could be cove lighting. - Thin light bars hidden by crown molding slightly lower than the ceiling. This can be accomplished using thin rigid led bars, rope lighting or fluorescent.

That way, you don't have to create more holes in the ceiling.

How do you intend to control the lighting? All from 1 or more switch(es)? Is dimming required/ important?