well, personally...try a travel agent. They can sometimes work magic! Yes, it's annoying that pop isn't included...but, juice, milk, choco milk, hot chocoalte..all included. You can buy a pop card if you're really desperate for soda...I don't receall ever actually missing it....
Extra expense...well...that all depends on what you want to do. For each location, plan to spend $50 - $150 / person on a shore excursion. They vary from shopping / historical tours, to swimming with dolphins. Generally, Ron and I always go for snorkelling / catamaran thing. Around $75 / person ish. Usually also includes booze and sometimes a meal / snack. You can get a list of shore excursion from carnival.com. They won't say how much they are, just how many $$$$, and you can guess from there. (this is where atravel agent can be helpful) Souveniers...depends on what you want to buy. Carival has a drink of the day everyday..always good, it's like $2.50 and you get to keep the cup
With the exception of alcohol...taking a cruise is great, as long as you participate. They have fun little game show / trivia type things ALL The time, and you can win a cheap little metal or trophey, make the video, or plain old just have fun. The shows are great...
What else can I say?? hmm...any other questions? did I spawn a new questions from all that?