Brass- if you are using 12V charging from the generator, that circuit is usually very low amps (like 4-ish). If that's all I used off my 8kw diesel gen (which is maybe 10-12), it wouldn't replace a days lost charge from TV & microwave usage almost no matter how long the gen runs.
You need about 20A (bare min) to 40A charge rate to bring two 12V batteries up in a reasonable time, for which you can run a 120V charger off the gen. Something like this one
If you have a charger built into your electrical panel on the trailer, you can read the specs on it and see if it has the capacity you need, or if you need to augment charging using somehting like the above. If you don't have the documentation on it, you can post the model# here and ask where to find the docs, as most are available someplace. I'm guessing that a 98 Prowler 30 feeter has a pretty cheap electrical center, won't have 3 stage charging (which is both better for the batteries and faster), and won't have the amps to do daily deep cycle recharging.
You're real best bet is to get temp power installed as fast as possible
, then rig a 30A trailer outlet near your rig, and go to a regular campsite type setup on your own lot. This will be way more convenient for ongoing construction as well. I've seen clever solutions for this where the permanent power was set up on the lot somewhere (instead of a one-piece 225A meter/main/load-center on the side of the future house) on a strut frame w/ meter/main + a small load center to run a 200A breaker to new interior panel in or on the house or garage; then run a 30A breaker off the small load center at the meter to accommodate the trailer outlet. Then construction (and extended camping) proceed off the permanent power, and Bob's your uncle.