I see 2 main issues that make you feel cautious.
First one: Wifey (and I kinda hate that nickname) and Jane are practically business partners. So if they start a full intimate loving sexual relationship, and it goes sour down the road, it could hurt the business. Is it worth the risk?
2nd: How much are you "allowed to know" about the developing intimacy and sex-having between the 2 women? That is totally up to you, your wife, and Jane. Just b/c Jane seems to have a sort of "don't ask don't tell" (DADT) thing with her bf does not mean you and wife need to.
All poly people decide on their own how much to share about their other partners with their other partners. Personally I have no big boundaries about that. My gf and I share most things, even sexual details. I like pretty much full disclosure. My gf likes to tell me a lot of things, and my bf sometimes shares a lot with me, sometimes neglects to share, just because it doesn't occur to him.
As well, some poly couples set boundaries on sexual things they are allowed to do with new lovers, or even longer term lovers. Some even have no oral, no penis in vagina (PIV) rules. Personally, I would HATE that. My gf and bf and I are all adults and are all allowed to do whatever with other partners as long as safer sex is practiced. Time sharing/management is more of an issue. Sex? Eh, go have fun! See you when you get back. Maybe you'll learn a new trick we can try!
Since you and your wife come from such a conservative background, you'll have to take babysteps. Just keep communicating! If DADT makes you nervous, DONT DO IT.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
me: Mags, 59, living with:
miss pixi, 37