Try find out what excursions the shop offers before hand and if possible do them on your own, you will save a bunch of money by not going through the ship, but if do go through the ship everything is taking care off, we have done one ship excursion and wouldn't do another through the ship, the rest we have done by walking off the ship. We have done several cruises and probably gonna do one this summer. Also highly recommend doing a walk out balcony, well worth it imho.
Just a quick example. On a trip to key west a jet ski excursion through carnival cruise was like $200 per person, we walked off the ship and it was $150 through the local person that does the ship excursions for them, walked a little further and it was even cheaper, walked a little further shopping and sight seeing and found the same jet ski excursion through the local place and it was $100 for all three of us.