Thanks everybody for the replies! I was thinking the same thing but wanted to run it by some other people as well. I have PM'd Rebecca and will send her the tablets today. She is going to talk with the vet tomorrow and will most likely be getting deworming meds for the 3 that she's taking in for surgery from the vet. Her neutered male house cat that she has at home could use the Drontal I'm sending though and maybe some of the ferals. She would have to grind it up and mix it with their food though. I suggested that she give the drontal one feral at a time so she could watch the one she's giving it to and make sure that only that cat eats the medicated food so no cat gets too much.
I did read that it is unsafe to give to pregnant or nursing cats so the one that just gave birth shouldn't get any until the kittens are weaned. My only concern is that the other feral cats 'could' be pregnant and though they are scheduled for surgery in May, what if they are too far along by then. I wouldn't want the babies to be harmed by the Drontal.
In any case, I'm sending the tablets along to her and have discussed all these things with her and she will be speaking with her vet tomorrow.
Thanks again for the replies.