The Caption is very highly rockered and maneuverable and was considered to be among the four or five best Royalex whitewater tandem open boats ever made. It could certainly handle the weight of your tandem team and a healthy load.
Air bags are like spare tires. You can absolutely do without them until you need them. On rivers, I will usually have at least small end bags in my boat. Fully swamped boats without any supplemental flotation can be quite difficult to rescue from current. If you are absolutely certain that you will never capsize in current, you don’t need them. Large air bags do not need to be fully inflated if you are carrying gear. leave them secured to the stems (where you don’t want the weight of gear anyway) and inflate them enough until your gear contains them.
Sure you can rip out the existing outfitting and install wood frame seats suspended from the gunwales on hangers. If you do this and want to keep the option to kneel, they will have to be suspended high enough off the hull floor to provide plenty of clearance for your feet and foot gear. You don’t want your feet hanging up beneath the seat if you capsize and need to make a quick exit.
Is this the best boat for your needs? Probably not. Will it work? Yes. But if this boat is in decent condition you might be able to sell it for considerably more than you paid for it and buy something potentially better suited rather than reoutfit it. For overnight trips on Class I-II water you might be better suited to a boat that is a little longer and tracks somewhat more eagerly.
If you do decide to reoutfit it, I or others can offer advice on sources for wood frame seats, hardware, seat positioning, and additional outfitting such as kneeling pads. If so, posting pictures of the boat with its existing outfitting would be helpful.