Best to communicate and figure out what you both want. Cuckolding may seem exciting when it is you fantasizing about it, but this does not sound like she is pursuing it for the same fantasy. Dating/friendship can lead to a lot stronger tie than just sex. Not that you have any say in what she does, but I’d think she is more than a bit interested if she wants to “give him a chance". And what about what he wants? Odds are he’s much more into a relationship than just hooking up - poke around this site too much and you’ll get lulled into thinking there are only bulls out there when really they are few and far between.
At least you all are upfront about the date with each other, just remember many more men are into it for sex at first - women want companionship and connection. Trust me I know, as years ago I pushed my now wife to date a co-worker who asked her out constantly. He was attractive, black, and I was all over her to cuck me after I found out she had a thing for the brothers and dated many in college. Looking back, my efforts were mostly to please me, and I just assumed she would get off the same way I did. Well, one date led to two, three and four, and soon I got what I want - a virile strong black man sleeping with my girlfriend on a regular basis. Of course I liked it. She really liked it, and so did he, but his intentions were never to be just the bull, and her most enjoyment was not in cucking of me, it was in connecting with him. It didn’t take long for her to leave me for him, and I ended up being the one on the outside. Had he not done some dumb things, and moved out of town the next year, I would have never gotten back in the picture. The fun and games part of it can happen, just don’t assume it will. I’d 100% recommend cucking if you know she’ll be with you and love you forever, though that’s impossible to guarantee. Instead, be prepared for her to leave you, for this guy or someone else.