Correction - RCL does not automatically add you gratuities unless you are using MTD. A bit of erroneous info here.
I think $100 per person per day is way high for spends.
You are going primarily to the Bahamas. You can grab a cab and go over to Atlantis. You can get some much cheaper excursions just down from the ship when you get off. You can do swimming with the dolphins ($$) and a bit of souviner (sp) in the straw market or on the main street.
Drinks are pricey but the grats for them are included in the price. You can't take any liquor or wine onboard an RCL ship I'm afraid.
The main dining room and buffet are included in the price you paid, so, unless you want to try the pay restaurant, you won't have extra charges for dining.
Pictures run around $20 a picture, so think carefully before buying. One from formal night is nice especially since it's your first cruise.