What I would do is have a permanent connection to the battery, run the wiring down to the front bumper grille or to underneath the front bumper or something, fit a water proof connector so you can plug it in easily. Mate of mine did it on his car that he used occasionally and it made it much easier to connect up.

I would only really worry about ventilation if the battery isn't a sealed type. Unsealed ones that you need to keep topped up can gas off a bit, especially if the cells are a bit weak.