Sodas: Free
Smoothies: $3.50~
Cocktails: $4.75 (Drink of day refill price) - $6.50 for most cocktails. Prices can vary depending on the drink but for the most part in the 5-6 dollar range.
Palo: $20/pp
Remy: $75/pp
Excursions: Best to check the disneycruise site for which excursions you'll want to do. Prices are listed and vary wildly.
Spa: Again, a huge list of treatments from hot shaves and haircuts to couples massages and facials. Massages are in the ~$110 dollar range for a single person depending on the type. A single day in the rainforest room (must do!) is only $15/day - $75/wk for unlimited use.
You are allowed to bring your own wine/alcohol on board unlike most cruise lines. If you bring a bottle to dinner there is a nominal corking fee.
No need to bring singles if you dont want - you can charge room service (and all) tips to your room account if you'd prefer to not carry cash.
Gratuity is automatically added to all bar purchases so dont feel the need to tip on every drink (unless you want)