Off boat storage is not really a viable option because I use them so often and at different places. The heat will not be excessive enough to damage them. The boat will be heated and, hopefully, will net get so cold as to crack the finish. If I leave the boat for any longer than a day during the winter I think I should drop my guitars at a band mates house. I may have to keep them in good cases with desiccants. Right now my main player is in a gig bag which makes it much easier to carry but provides much less protection.
Getting a road case for my amp is also a good idea. kd3pc, your kid has good guitars. My nicer acoustic is a Guild that I bought new back in 1981.