good advice except don't forget to tell her that it costs 5 BUCKS to use the ATM on board.
In answer to your question Sassy, alot depends to how much booze and soda you plan to consume, how many pictures you plan to buy, and your wise assertion about shore excursions. Drinks are usually about $5, sodas $2, 8X10 photos $20. SDo estimate from there. Also don't forget they will charge you $10 per day per adult for tips. You always have the right to cancel the charges and pay your own tips, but be aware they are going to do that.