Hello, an American-Canadian here... here are my thoughts:
1) I think both of those sounds fine. I might also say "Next week I'll get back on track." meaning back to my normal routine (or at least what I want my routine to be).
2) I might say "We will (or 'are going to') have the floors/flooring replaced in the bathroom, the kids' room, and my room." and "We will have porcelain tile (not need for 'floor') laid in the kids' room and my room." Saying "the kids' room and mine" is ok, but it could be interpreted that you and the kids share the same room.
3) 'Ceramic tile floor' is the floor itself - "My bathroom has a ceramic tile floor." 'Ceramic tile' is what is covering the floor - "We are putting ceramic tile in the bathroom". I wouldn't use 'ceramic flooring', but 'ceramic tile' instead.
4) Both are fine. "This is (pretty) lame." sounds more like like disappointment, whereas "This is bullshit" sounds more angry. It depends on how you and your friends usually talk to each other.
5) Yes, both uses work. Being picky in that first sentence, I would say "Step back or you will get wet." :-)