Semi-permanent parking

what is the electrical capacity of the RV? If it's 50amp, your solution will not work.

Need to look up the charts for distance and loads to determine wire size. the proper way to do this would be underground buried wire (or conduit).

If you're determined to use temporary wire, then make up a proper size cable with the connectors on the end.

I feel the pain the family is having with Tom. We're having our own issues. While nursing homes are generally very bad, medicare will pay for long term care.

Sewer & water?
I think you can buy 100' RV extension cords, just not cheap. But neither is two 50'. IF you do get the two 50', there is an extension cord connection cover box I found on Amazon for about $10.
You might want to consider a closer spot to save $$ on cables, less voltage loss, and closer to the main house.

Buy welding cable with the correct ends installed.

I just hired an electritian to run power 70 feet for me, I dug the trench to meet code, his charge including all materials was $275. You may want to investigate what it might cost to do it correctly rather than run power cables on the ground.

Extension cords on the ground long term isn’t a good plan. Will your local government allow this...electrical or even living in an RV? (Zoning)

X2 have it run under ground,

Underground is better.
2 ft under, with vertical rise (preferably in conduit) where it ends near the trailer. You can do it yourself, or hire some low-cost electrician for a piece of mind. You need a conduit only for a rise, not for undeground. One cable all the way, no 2*50 cords.

To determine the cable gauge that you need, run the numbers for anticipated loads (i.e. maximum amps) on 100ft distance. If A/C is not planned, microwave will draw up to 12A, other loads are minor, you total current will be under 30A then.

You might need a junction box near trailer to go from a beefy undeground cable to a thinner wire that you would terminate with RV plug, but this is only if undeground is really thick - I don't remember max diameter that fits RV plug, is it #6 or smaller.

Home Depot have aluminum cable suitable for underground works with gauge up to #0, but you won't need it that beefy.