Feral cat/kitten spay neuter after care?

I pick up Feral, mama & kitten, this afternoon from the shelter after spay/neuter. They will be in separate carriers. What after care do they require and how long until I can release them? I have dogs and this is new to me. I live in Palm Desert and if there is anyone out there who would like to assist in trapping the balance of the colony in my neighbourhood (Westfield Mall) for spay/neuter/release, I'd love to hear from you. Thank you!