many buns don’t like hardwood floors, so people use large, cheap area rugs or runners to give them footing. after awhile, you might be able to decrease the number of rugs and they’ll learn to be okay on the hardwood. they’ll figure out how to walk without sliding all over.
i agree that the bigger the area they have, the better… like hooty said. but i also know that it’s nice for them to be able to come out and play. that will increase their interaction with you and make them feel more a part of the family… have you been able to bunny-proof an area for them to play in yet? what are your hesitations in allowing them outside-the-pen playtime? many people cannot allow their buns absolute free-roam, and that’s okay. oftentimes, bedrooms, computers rooms, etc. need to be placed off-limits. can you start with having one room that is safe (ideally the room they are housed in!) and see how they do?