I don't blame you for being freaked out, since your son's safety is a priority. Has Dutch ever done anything like that before? I know my pup went through a phase when he was younger where he'd bark at my DH in similar situations, but it was over in a second with lots of tail wagging and happy whining. If it had been a hard stare and ignoring me, then I'd be worried about it too.
Are there any OB classes you can get your son and dog together to participate in? That's my first suggestion, without knowing anything about their relationship. I guess my next suggestion would be to try to watch for signs that Dutch may be looking to climb the social ladder, and then knock those rungs right out from under him. If he's claiming the bed as his territory, then he absolutely cannot be allowed on the bed. If he's claiming your bedroom, then unfortunately that area is off limits too. Good luck with getting to the bottom of this. Dutch is still a puppy, so now's the time to nip it in the bud.