JC, I know you are not far from me,so if you are going on a head boat I suggest the following.
I've fished on head boats for tuna in the canyons,first off you will most likely fishing for yellowfins,not bluefins.
Most of the head boats like the Doris Mae,(Barnegat) Big Jamaca (Brielle) take out 25- 30 passengers.This type of fishing is not like on a a charter boat,to have the best chance of landing a fish you need 80 lb test.Most headboats do not allow braid for the reason mentioned above,mono only.
A Penn 30 TW would be minimal,best bet would be a 50TW with the 30 for jiggin tuna.Also bring a lighter stick with some squid jigs.Putting down a live squid is like candy,and it won't be long before you hook up if the fish are there,you can also use this lighter stick if the mahi come into the slick,just put on a small chunk and you'll have mahi for dinner.
PS The Canyon fishing has been pretty good of late,most fish have been in the 70-100 lb range and alot of Big eyes have been caught as well as quite a few swords.If you want to try for swords fish deeper and use wire or 130 mon leader. Good luck and let us know how you made out.I'm probably going after the 15 of this month.