I am so pleased that you are going to get them both done - mammary cancer, as the above article shows, does take years to develop and normally after repeated unbred heats, so if done after she has weaned these kittens, there probably isnt' much concern - but do check her mammary glands on a regular basis (just as you would check your own for any changes). Spaying takes one of the major, more immediate, risks, pyometra, away. And as I said before, males can produce sperm for up to 6 weeks after being done, and females can get pregnant as soon as a week after giving birth, so do keep them separate, esp as mums dont tend to like whole males around the kittens, and may be a bit snappy towards him, you dont want her being stressed too much.