Connect or disconnect
For the reasons already stated, I would prefer to see the untended battery charger and shore power disconnected.
However, if you are concerned about maintaining an operational 12V bilge pump - you may choose to install a little "Battery Tender" type maintainer/charger (ie: Guest #2602/2603), in lieu of the 25A charger. The 2602 only puts out about 0.6 Amps, and is not likely to boil off your electrolyte.
Also, make provision to have someone monitor the boat, and report & deal with any problems.