Weaning kittens question

I haven't weaned kittens in so long that I've forgotten how (duh).

Anyway, here's the situation: I was trapping some strays for trap/neuter/release this weekend when I found four kittens in a garage. I decided to take them and try to trap their mom, as I was afraid she would move them to a potentially dangerous spot if I didn't take them (I was trapping in a part of town with many stray dogs). However, I was lucky enough to trap a very unhappy little black mother cat later in the day.

Since I didn't know if I would manage to trap the mom cat, I gave the kittens some KMR from a bottle, then offered them a saucer of KMR with some Hill's a/d mixed in. Their teeth were just beginning to come in, so I thought this would be the only food they could manage.

All four of them were able to eat/drink the KMR mixture out of the saucer, thankfully, so I am now serving this up in the condo where I'm keeping the family.

Should I be offering other foods to them?

Maybe the black mother cat will accept the kittens you have as fosters. I've heard it said that mom cats will take care of each others kittens.

Actually she has accepted them - I'm hoping she's the real mom. Sorry I wasn't clear about this. I'm assuming all kittens need to be weaned eventually; I'd just forgotten how and when.