The good thing here is this isn't a I gotta have them right now type situation. Keep the water up in your batteries (only distilled) and keep them charged and the OP should have plenty of time to figure out their needs and what battery fits them.
Btw The single Interstate grp 27 that we run the trailer with is 3 years old and still a happy camper. The 8-D we use for the inverter has the AHs to slap ALL the other children around and laugh about it. That is if you have the room and can lift it. lol