On a party boat you have a rail to help (if not seeking a record) but you have a lot of hull below you. I would suggest looking at a 7 foot rod if you have that must buy flowing through your blood. You can get away with short rods but when you hook a fish running under and around the boat the length will be more than welcomed, but many including some so called experts like 5'6" rods. Some guys swear by roller guides but on a party boat your fish may be running you around a bit more so I would caution against it.
If I were you, I would use what you have the first trip. Something that will handle 100You will get a feel for what your doing and hopefully for how you handle a few fish. You will know what suits you better with experience.
If you have to buy something then your on the right track . Calstar 700 H is a nice party boat rod that's been used for a while too, you may be able to find a used one now at a good price.