From what I understand from the OP, the boyfriend didn't actually cancel the plans with her, he brought up the family-friend visit and waited to see if hbandtr4eva would allow him to back out of the dinner with her. She did not, and then he tried to guilt-trip her. I'm still not clear as to whether he ultimately did say, "Sorry, but this family dinner has to take precedence" or if the OP has put her foot down.
I don't see a problem with him posing the dilemma to the OP. What I do have a problem with is the guilt trip afterward. If the boyfriend told his folks that he had plans and the parents pressed him to cancel, then I also have a problem with that - but if he even remotely said, "Well, I have plans with hbandtr4eva, but I can probably get out of it" then I absolve his parents of wrongdoing. Unfortunately we don't know what BF told his parents, and it's likely that hbandtr4eva doesn't either, if the conversation didn't happen in her presence.
In general, when my husband and I were first together and he had something come up that conflicted with plans we had together, he'd bring it up to me and if I didn't excuse him (which I'm generally cool with if said plans were not something structured involving something like tickets - I'm pretty flexible, really) then the subject was closed. He wouldn't push the issue, which I appreciated.
In the situation described by the OP, and let's say that I planned to cook, and the groceries are already bought, and my boyfriend presented me with this conflict, I'd explain that it would not be possible to move dinner but that I would be willing to compromise by releasing him from our evening afterward so that he could meet the family and friends for dessert and coffee - I'd probably even be willing to shift the dinner hour a bit earlier to accommodate. A bit of compromise isn't a bad thing.