No captains license required unless you are chartering for money and you are under certain tonnage.
Some insurance companies will require captains sign-off, especially if you are jumping into a much larger vessel (which we are) or are first time boaters jumping into a large vessel.
I have received three quotes from insurance companies and none are requiring captains training to move up, however, the captain that has been helping with our sea trials on the past two boats is a close friend and will gladly ride along and provide guidance if necessary. My wife and I have been boating since the early 1980's. We are well versed in navigating the river (and beyond), it will just help with some of the onboard systems and how they integrate with each other as much as anything.