My grandson had just started potty training a few weeks before our trip last year. He was 2 at the time. Bad timing, I agree, but he started self training and we could hardly say no, don't learn that yet. I don't think he would've quite understood the concept of if you leave the line to go do what we've bragging on you for weeks now- you're going to be punished.
I can assure you, if your husband blocked my daughters way back to me after taking him to the potty, I'd just get a CM and see what they say. Potty breaks have long been an accepted practice for the younger set. I'd be ashamed to raise a fuss with someone who took their toddler to go to the bathroom and just wanted back where they were.
Thankfully people are a lot tougher on the internet than they are in person. Not once have we ever had anyone be anything but polite and easy to deal with as far as potty breaks.
Seriously, relax people. It's just a character meet n greet-so what if someone gets away with something now and then. Who cares....or as they say...Let it go...