Never done it or seen it, but I like it.

They would have to have their own Transfer Switches.

I'm wondering if you are allowed to tie two separate loads to one set of Generator lugs... unless the Generator has Load1 AND Load2... and they are split evenly?
Like I said, I've never done it..

I'm thinking... feed a panel(outside, or in a shack) and sub-feed the two Transfer Switches from there..

There is another Generator topic, where the neutral was brought up... If the Generator has it's own main ground and bonded neutral, then the neutral needs to be switched in the Transfer Switch along with the feeds. 4 pole breaker in your case.

Anyways, a few things to run by Inspector.

I'm interested to know how this will turn out
Good luck.