Sorry for any redundancies, but I've read tons of posts and I haven't found answers to my specific questions!

We're scheduled to start renovations this coming Tuesday. Our bathroom is going to be completely gutted, although layout isn't going to change. The building we live in is 100 years old this year. We're replacing the original, broken, 1 inch hex tiles with carrara 1 inch hex tiles with some as yet to be determined shade of gray grout, putting in subway tiles on the walls (chair rail height everywhere except by the tub, and stacked not staggered for a bit more contemporary look), having our clawfoot tub reglazed with a charcoal color on the outside and white (or possibly silver?) feet, replacing the sink with a more modern vanity that will give us some storage, etc. I guess we're going for a vintage modern mix! :)

My questions:

The hex tiles we bought have exactly 1/8 inch spaces between them, and a little less in some places. Everything I've read says unsanded grout for 1/8 or less, sanded for 1/8 or bigger. But what about exactly 1/8?? The marble is honed, so I'm not overly concerned about damaging the finish. I'm more concerned with shrinking cracking grout! I've tried to talk with people at local tile shops and gotten opposing answers. What do you think? Is there a specific brand of grout you recommend? Sanded or unsanded? I guess I'm leaning toward sanded based off everything I've read, but I really have no experience with this! We live in nyc, so I'm sure someone nearby will carry what we need--I just don't know what that is yet!

Also what about sealant? I think we want to use some sort of penetrating sealant, because obviously we're not going for the polished look. But what kind works best on honed marble? I have a toddler, so we definitely want some sort of sealant.

We're going to use a white, unsanded grout for the subway tiles on the walls. They'll be stacked against each other, so small grout lines. Can we use the same sealant for that grout that we use for the floors?

Thanks!!