They’d have to get him to Bobby’s, first! They took a road trip to Rufus’s cabin for the setup, knowing she wouldn’t fall for the trick at Bobby’s place.
He probably would have knocked down most of the cabin if Cas didn’t fix him, simply because he had no place to go, and no doors big enough to crawl out of. All scrunched in a corner, and the only reason he couldn’t try and stop Celeste himself was because of the pain he was in from his bones expanding.
((There’s a good reason the victims of her curse often are unconscious for the good part of a week after it hits. Extremely compacted, extremely fast.))
The main thing about the Lounge is, Gabriel buffered it for size different interactions. The borrowers can’t be deafened if you yell, and no one can get hurt. Sam and Dean wouldn’t have that luxury. They’d need an interpreter, at least at first, someone who can talk to each of them separately.
I’m pretty sure Bowman would be all sorts of offended if he hears Dean is more giant than his giant now. Considering how serious the problem is in Wellwood, Bobby would definitely hit the road to help.