If they are doing that much work with them he should do just fine.. might have them place your litter box near them for day or two, so it gets used and will have that scent to start his in house training.. my yeti cat came from a semi-feral mom(ie a wood pile cat) he is better about covering things up then some of our older girls.. get a stuffed kitten toy around his same size so he will a "buddy" this has worked for us in the past...
yeti cat: two toes short of the record books
eons ago there must had been a creature with a roar
like a vacuum cleaner, it most likely ate cats.
smokey,yeti, pansy, violet, ember and brullie
jolene, tammi and emma the ghost kitties in the house