Haven't been for dinner, but we had breakfast there twice last week when we stayed at the WL, and it was, as posted above, the best deal on Disney property. It is very, very casual, and I too think that may not be quite the spot for birthday celebration. Nothing at all wrong with the place, but I know I myself might prefer something else.
It is a very short boat ride from the WL and then a very short walk from marina to Trail's End.
It was a treat for us to see the peacocks strolling on the roof of the tavern as we were leaving to head for the boat. I gather this is a daily occurrence.
If you haven't tried Ohana at the Polynesian, it was the highlight of our trip last week, as far as dining was concerned. We had a great table at the window and saw the fireworks go off at MK. Sound is piped in and you feel as if you are right there, just minus the elbow to elbow people. Steak, shrimp, turkey and pork are served there. It is a very festive restaurant.
If you decide on Trail's End, you will enjoy your meal. Good luck with your decision.