I'm very familiar with Marina del Mar as we always hang out at Coconuts, the restaurant/bar that all the divers and boaters frequent right next door. We have stayed in lots of places over the years from Islamorada to Miami.
I've booked a room for a week at Marina del Mar in June. As you may know, most of the hotels in Key Largo in that price range, while not certifiable "dumps", aren't going to look like $150 rooms you might find elsewhere. The hotels in that price range are almost always older properties and might look a little worn. My wife and I call it that "keys" look. You won't get anything that looks like a new "resort-type" until you get up to the $200 range, which is why they don't allow pets.
I'm a dog lover myself, but I hope you realize that any place that allows pets is not going to be pristine. Pets have hair (and accidents) and it takes a super human effort to keep a place in top condition after animals have inhabited that space. Anyone who has ever owned rental income property knows this. IMO, I think you'd like Marina del Mar. It's as nice as you can get considering they accomodate pets.