Threesome

So me and my ex partner are still really close and he said he wants to have a threesome but only with me and another girl and he’s letting me chose. He wants to see me and her fuck each other is why it has to be a girl. He said he doesn’t know if he’ll really fuck her it depends but if he does he would wear a condom with her and do me raw but if so would it be ok for me to set limits for him and her ? I wouldn’t want him enjoying her more than I is all. I don’t know how I feel about this though because I love this man. Although a threesome is also a fantasy of mine. I need advice over this please on how to pull through or how to play it safe without feeling hurt over it.