On the first question, of course either will work but the tender is easier since you can connect it either directly to the charging post and ground under the hood or via a hot cigarette lighter outlet and just leave it alone. The charger usually requires you to turn it on and off or otherwise make sure it isn't overcharging and comes on when needed if the battery is draining. I own both and for the use you described I would use the tender. If the battery was low/drained, I would put it on the charger until fully charged, then switch to the tender.