Keep in mind Bingo, if you want to play, and tips. Tips for Palo servers, and gratuity if you are putting them on your shipboard account. Plus the cost of Palo if you dine there, and you should
Also, although not expensive, if you need any medicine (my husband needed cold medicine on our Med), the infirmary does charge.
On a 7 day, you might want to do a class or two that has a nominal upcharge...I know you said you aren't big drinkers, but there are alcohol tastings, my favorite is the Martinis (you can't get me near the whiskey tasting, yuck).
We usually don't buy pictures, but we did on our first cruise and that was about $150. Now, we'll buy one or two, or just rely on the hundreds we took ourselves! It is nice to get family photographs though, and you can do portraits onboard too.
The Cove coffee costs, although the snacks are free. I don't drink coffee but love a nice hot chocolate in that quiet environment!
I don't give my kids specific limits, but warn them to be careful, and they are. They usually will buy a smoothie or two, some movie candy, little things like that.
It sounds like you have a very good plan. The gift shops are tempting, lots of fun stuff in there that you can't buy elsewhere, and on
Castaway Cay