Threesome in a relationship

Hi everyone! My boyfriend and I are considering trying a threesome, once with a guy and once with a girl. Any suggestions? We've been together for three years and are now living together after doing long distance. This wouldn't be for a while so we can enjoy living together and making sure we'd both be alright with it. We've discussed ground rules and how the other would feel when one of us is doing something with the guy or girl. He's much more excited for me to be with the girl, but he's still open to having a guy as well. Have any of y'all done this? How did it go for you?