IMHO Emergencies are just that -- must have's period. This is a clear case of where a smart charger will do the job because you will be on shore power, not a generator.
But a tiny charger ain't gonna cut it.
If you need the rig's heater and night this may make things more challenging. A supplemental AC heater will allow you to satisfy your needs with a smaller, more affordable smart charger.
You do not need full batteries in the morning. you need enough charge to allow your rig to start and then charge while you drive. A 25 - 40 amp smart charger would be plenty, even if you use the rig's heater.