My wife unknowingly drank my cum!

I was feeling horny and naughty. My wife won't let me cum in her mouth so I decided to make her a cup of coffee with a half load of my cum in it. It's the first time I've done this so I was a bit worried she would notice the taste. She didn't. She even said it was a good cup of coffee! Watching her drink up my cum without her knowing was super hot. Definitely won't be the last time I do it.
It's now got me thinking about doing this for my hot sisters-in-law.
Anyone got any recipe ideas?