We did a B2B on Adventure in February and another B2B on her in April. DW has mobility issues, and she never had any problem navigating anywhere on the ship - including the Casino (but that's probably because we walked out of the Casino with about $500 more than we walked in with on both B2Bs). π The casino can get a bit congested around the slot machines, but from what we've seen, that is more because some people think that they are the only ones there and that their family can block the aisles while watching them lose their money.
We have B3B's booked on Adventure in July and October, and love the ship.