An answer to a question please?

Yep, will need to run generator for few hours each day to recharge the batteries. As noted, will need a decent house battery bank to power the inverter to run the fridge when not on shore power or running the generator.

Another option is to install a sufficient solar panel set up to keep the batteries charged. Even so, will need to run generator some if in shade or on cloudy days.

They will likely be able to dry camp without issue as long as running their generator from time to time is OK. Depending upon how they use the coach and what goodies they want to use the generator will likely need to be run a bit at night so they can watch TV and cook and this will keep the batteries charged before going to bed. There should be plenty of battery power to keep the fridge running over night and since you are going to need power for the coffee maker and breakfast, running the generator for a few hours in the morning will get the batteries charged back up again. Solar can help with the morning but won't help at all for the evening hours so a generator is still going to be necessary to some degree.

Yes we have 6 batteries to run the fridge and other items
if the batteries run down they can run their generator and charge them back up

Thank you ScottG and wrgrs50s. I appreciate the info.
Now we'll be comfortable asking them to join us at the lake!??

His only limits in boondocking is the size of his battery bank.
Solar may be an option.

Thank you! So boondocking is not out of question?
We boondock at the lake and mountains and we want them to join us but we're concerned they couldn't because of the fridge.
Thank you again, Okie

The newer motorhomes and 5rs that have the residential fridge have an inverter installed that is dedicated to the fridge. It supplies 110 to the fridge from a battery.