I have been thinking, yep I know that is dangerous, using your description of time of using the generator.
If one started with a full tank of fuel (100 gals. in your case) and I did some figuring.
Arriving at 4pm Thursday and staying until 8am Monday would be 88 hours of running time on the generator.
Most generators use .5 gal of fuel per hour with a light load. That would be 44 gals of fuel used.
If the load was heavier, the most I have used per hour running our generators in the last two motorhomes using both air conditioners, we used 3/4 gal (.75gph) according to my figures.
So using the heavy load figure of .75gph one would use 66 gallons of fuel.
In both cases you would have enough fuel for the term of your stay since at the 1/4 level of the tank you have 75 gallons of fuel available to run the generator if you started with a full tank.
Of course the other option would be to install a 150 gallon fuel tank like I have in my chassis, it gives me 112.5 gallons available at the 1/4 level.
The DW says it is like taking out a loan when we fill it.