Litter Training and Roaming advise!

Okay so we have our new baby holland buck (still nameless) and I am asking these questions in preparation. We currently live in a huge house but we are moving this weekend and downsizing to half the living space. So I have not let our new bun roam on his own yet as individual rooms are packed and sanitized.

Once we move, bun and his cage will be in my two youngest daughters room. They have bunk beds and a dresser. We would be keeping the buns cage on the floor or even the closet floor.

My question is, should I be relying on him to go back to his cage to go to the bathroom or should I have a separate litter box for the room? And this place has nice new plush carpet. Should I be getting a large blanket for the floor? And since he is only 9 weeks old and not litter trained yet, will he be peeing all over the carpet? Should I wait for him to be litter trained before letting him roam? Would putting a blanket out make him want to pee on it since it's absorbant?

Thanks for any advice in advance!

I would limit his space at first and slowly give him more freedom as he uses the box in his cage. At the beginning our boy liked to pee on anything soft...so I moved blankets and pillows. We have a couple litter boxes on the main floor, but he only uses one. Once he was neutered he was much better at using his box.

I read somewhere that bunnys can't be completely box trained until 4 months... I'm not sure if that's true though! Until he's box trained not to pee out of his box (bunny poo is an easy clean up) I would probably only let him out of his cage in an area he can't ruin anything... do you have any tiled/linoleum/wood floor? my girls spend most of their time in my room (by choice) which is hardwood and they don't mind. they also like laying in the kitchen which is tile so buns get used to the hard surface and when they were being potty trained keeping them in those areas really helped with mess!
good luck in the new place!