The extra adult fee always annoys me. How exactly different is it for your 18 year old to be sleeping in a space one night for no extra charge, but once the kid is 19, sleeping in the same bed/space, it suddenly costs more for the room? It's most likely an advertising gimmick, so hotels can say "kids 18 and under stay free!" and draw in more business, but honestly, a room for 4 is a room for 4- doesn't cost more for anyone to sleep in that space.
Southwest EBCI? We stretch that. If it's just DH and me or just DD and me, we buy one EBCI and the check-in the 2nd person at the 24 hour mark. If it's all 3 of us traveling, we buy 2 EBCIs. I always take the seat I want and figure that nobody is going to want the middle seat next to me anyhow. (or DD takes the window, I take the aisle, and we wait on the middle seat for DH, once again figuring that nobody is really going to want that middle seat anyhow). I would not buy one EBCI and assume I can hold the entire row. I might try it, if it didn't matter where we sat, hoping for the best, but there's no way I'd then say "this seat and that seat are saved." I'd just figure "lesson learned" and let the other two family members sit wherever there's space.
Lying about a kid's age at a buffet... Ultimately stealing, but I see how it's hard when you have a kid who eats like a bird. My niece is extremely small for her age and has always had a tiny appetite. My sister would lie about her age at buffets until she was about 12. She simply didn't eat enough food for my sister to be able to justify the price. I know... if you can't afford to pay for it, eat somewhere else, but not everyone thinks that way. Some people think Disney is taking advantage of families by charging 10 year olds as adults (and I actually agree with that, but I don't know if I would have lied about DD's age to save money at the buffets. Never was an issue for us, though, but I can see where parents are tempted).