Also agree with: 1 letting the shore power charge it, presuming your battery charger will handle it, is wired to charge the various battery banks; 2 charging the battery separately either with the battery charger aboard or a separate battery charger or ashore; 3 jumping the engine using a small, portable power pack; 4 charging the batteries with your genset (same as shore power, if it will start with the batteries you've got); 5 arranging your collection of battery switches so that you can start with any of the batteries you have aboard.
All these alternatives have their own caveats. Charge rate, float rate, different types of batteries. Safety issues including off gassing, sparking, boiling, wire size, other electronic goodies.
I have to wonder about using the house breaker panel battery switch to charge a dead battery. Speed and wire capacity, let alone discharging the good bank to attempt charging the dead...
But for the short term, a jump start and a charge, any of the above will be fine. And the easiest, quickest for you is best.
And for the long term, wiring, switching, fusing, charging, etc., needs to be worked out so that silly errors and ageing batteries still allow you alternatives to get going. (Continuing my past summer's adventures, I now cannot charge my house bank with engine power, nor can I start an engine w/o its own battery (or jumping from another bank).)