I think Dean is very similar to Meg. So he'd probably the same way with the kids as Meg is. The Megstiel kids would probably have him as their favorite Uncle cause he lets them get away with stuff that Castiel wouldn't normally let them do, like eating sweets before dinner. But then Sam is probably the kind of Uncle that reads them bedtimes stories and tucks them in bed when he and Dean babysit so it's a tough call.
I disagree. Sam would be the one to let them run around the bunker because what’s the worst that could happen, they’re just having fun and Dean would be the one to freak out and try to get the half-demon, half-angel kids under control before they burn something down, are you kidding me right now Sam, we can’t lose sight of them.
Really? Deans /cares/ for Castiel an all but if he found out they had kids, and he heard the legends behind the kids. He would spend his time figuring out how to kill them and claim it’s for “castiels own good.”