The ultimate meaning is they didn’t have dinner. But, it could mean they never arrived at the destination for dinner, or dinner was never served, or that they ran out of time, or got sidetracked. There isn’t enough information to determine exactly what happened. If this was a conversation I was having with a friend, I would assume something came up that took their attention. They got so involved in something that grabbed their attention that they forgot about dinner or were too late to have dinner. I am an American English native speaker with absolutely no experience teaching language.

There could be some more nuance to it but I'll try to answer. If they never got to dinner, it could be that they didn't progress far enough into their meal to reach dinner. For example before dinner you might eat appetizers. If the power goes out at the restaurant while you're eating your appetizer, you may not end up being able to receive dinner after. Therefore, you didn't get to/end up at dinner. Another situation would be if you missed your reservations altogether and didn't end up arriving at the place you were going to have dinner.

As Kathleen said, there is not enough context to be sure. Given the context, there is a possible ( or in fact probable ) dirtier interpretation that nobody has yet mentioned. Since it was an anniversary celebration, it is quite possible that they got distracted doing something else, and forgot to eat dinner. I will leave it to you to guess what I mean.

Get to means get around to. [get around to something] to do something after you have intended to do it for some time. We have to get around to cleaning those windows. To start doing something:begin, start on, set about. Source: https://www.macmillandictionary.com/us/dictionary/american/get-around-to

Well we never actually got there means that they never arrived there. Get can mean arrive Hope this helps