[MFF] My wife gave me a threesome for my birthday

My wife and I have been together 10 years this year. This story takes place in March of 2018. Intro’s and Descriptions for the imaginative readers:
Me – 36M, 6’3” 235LBS, athletic build, slightly above average length and girth
Dee(wife) – 33F, 5’11” 140LBS, keeps things tight, fake boobs, black hair and legs for days

Dee has always been open to trying things in the bedroom, never has she been shy or bashful about what we do behind closed doors. However, she is also a bit of a submissive, so she tends to not ever push the envelope herself. This honestly took me about 5 or 6 years to figure out. We are best friends and love each other unconditionally, however she always made a point to tell me (usually when rumors of affairs of people we know started circulating) to always tell her if I ever got bored, that she would “figure it out.” I never really knew what she meant by that, and my upbringing and social morals told me to not ponder too hard.