I use this rig from driftmaster, link at top of page, and love it. Three screws and you are in business, 6 screws for you and your 12 year old.
100 % adjustable.
In my opinion if you are tournament fishing you need a gps. A Garmin hand help is fine.
It is easier to long line from the back of the boat, if you plan on doing any of that. Do some experimenting, without boring holes, as to where the rod holders should be mounted. In the front watch for trolling motor clearance
and ease of docking and undocking the trolling motor when the holders are in place.
Rear placement for pulling in a bassboat is sometimes tricky ( for two people to manage them) Make sure where you want the set up and just buy an extra set of star bases. Move the 4 pole mount as needed. They are very easy to move and remove.
I am fishing form a 17 ft. bassboat. Bottom line. decide whether you are going to fish two in front or not. Get the seating set up right, then mount the rod holders so they can be properly managed, in a comfortable position for an 8 hour day of fishing.
That means, getting to bait, both artifical and live, netting fish, culling fish, running the trolling motor.
good luck.