We took our 3 kids, ds 12, ds 9 and dd2. They loved it. Our server was just great with them; took time to explain to them all about tea, gave them different choices of sandwiches and desserts, etc. The boys couldn't decide whether to get the Mrs. Potts tea or an adult selection, because they wanted real tea, not chocolate milk. So she sort of custom made theirs. She thought they may not enjoy the smoked salmon, cucumber and other types of sandwiches and asked if they would prefer egg, chicken salad, or cheese. IT was very nice. We got the Buckingham Palace tea if I remember correctly, and it came with 3 or 4 varieities of sandwiches, scones with cream, some little pastry things, and choice of dessert - we had strawberries & cream - yum!
The boys wore polo type shirts and khaki shorts and dd wore her princess dress, though a regular sundress would have been just fine. I wore a skort. No fancy gloves or hat lol. We were surprised that the boys both said next time we go to WDW they want to go to tea, not once but twice!