Hi See! – I have dealt with wild rabbit kits twice before.. my experiences were this – no rescue/shelter/humane society, would touch them – they simply too taxed out, on other animals, I suppose… anyhow.. I offered both litters cats formula, in bottles, but, both, seemed to be past that… I kept them in cardboard box, with felt scraps on one side, and hay on the other, and dropped in rabbit pellets..they seemed to be eating those fine,, after about a week or 2 ( different sizes of the litters ) – I released them all I the same place, – a safe farm of my uncles.. I hope they all thrived – I hope yours do, also 
ETA – just reread your post… ” sneaking in ” the babies,.. is a pretty wild card situation.. no telling how that will wind up.. it could work… it couldn’t.. if you attempt this, plz… be on hand, to intervene tho.. maybe she will accept… perhaps not.. wild rabbits, are different breed, as tame rabbits, but.. lol… ever seen youtubes of a dog nursing a deer? xD It could work, just – be careful!