50 amp generator

real workl a 5-6kw generator is all you *need*. 1.2kw is 10 amps, so a 50 amp generator (single 120 feed) is 6kw. The 50 amp input on your trailer is 2 120 volt 50 amp feeds, so a 6kw generator is only 50% of the *max* power, but real world 5kw runs 2 ac's with power to spare. Most of us are camping (non ac) on ~2kw, parallel 2kw or a 3kw gets an AC, parallel 3k gets almost everything. It is far cheaper to heat both air and water with propane then burn gas to make electricity to make heat.
A 30 amp to 50 amp *dogbone* style adapter will take you from a reasonable generator to a 50 amp trailer input. If you really want all 50 amps, you are looking 12kw+ generator.