Re: which gnerator to purchase?
Do you have 1 A/C unit or 2? Is the trailer 30amp or 50amp? In the first case, you will probably want between 3 and 4KW. In the latter case, probably between 6 and 9KW to fully power it, or you can run it on less if you only run some stuff at the same time (only 1 A/C at a time, for instance).
I had a Honda EU3000 generator for my 30 amp trailer, which was a very good choice. At first, it would not start the A/C reliably, but I installed an easy start kit in the A/C, and didn't have any problems after that, but did need to be careful what big current users were running at the same time. The Honda was very quiet, produced very clean power (most other generators produce a 'modified square wave' which bothers some electrical devices) and was fairly fuel efficient.
2 EU2000 Hondas hooked together is a very popular choice. They will fully run a 30amp trailer, are quiet, small and light. And if you aren't using a lot of power, you can run just one of them. The EU3000 is bigger and heavier, but does have electric start. Plus I imagine that if you used 2 of the EU3000 hooked together, you could perhaps run a 50amp trailer without too much trouble. There is also a EU6500 which might be even better for a 50amp RV.
There are a few other 'ultra quiet' generators which might be a bit less money, and may even approach the Hondas for quality. Anything other than 'ultra quiet' is questionable for RV use, due to the annoyance factor for your neighbors. And it is hard to beat the Honda quality.