i love fitteds + covers. I don't think its too tricky. You can always prepare them in the nappy bag (fitted inside cover) so the carer knows what goes with what.
Thats what I do for mum She prefers that to trying to fight with flats & covers! lol. You must lose the nack
She does usually get the gist of it now. She's even been known to chuck a flat inside a pocket out of desperation. She's getting handy at these new fandangled nappies