I hope I can get some advice rapidly. I have two major concerns:

1) We selected natural slate tiles (12x12) for our 25 sq ft. bathroom floor. The installer is coming next week. When I looked at the tiles today I noticed that small chips (1/8" to 1/4" approx) of slate come off fairly easily with a finger nail flick etc... I am worried that the slate will continue to flake and cause chips to get on people's feet and scratch the tub & wood floors around the house. A guy at the tile store said he thinks the penetrating sealant will stop it, but I am skeptical.

2) The slate naturally has significant thickness variation within a given tile. I am concerned about the sensibility of having edges of 1/16 to as large as 1/8" to stub toes on. I am worried this is a bad idea for a bathroom where people are frequently barefoot.

I'd like to be able to give the installer as much notice as possible if we need to reconsider.

Your input & guidance is HUGELY appreciate!
Have a great day.