Help needed please to introduce my gf to idea - guys and girls pls!!!!

Hi,

I'm 29 with a gorgeous 23 year old girlfriend, we have been together for 1 year and I would love to fantise with her first then hopefully see her with her first black man. I have not disscussed the idea with her outright but we have discussed black guys in a pretty casual way and she had a black boyfriend when she was 19 who she didnt relax with when I asked her why she said it was because 'he was too big and black' so it sounds like she definetly saw his cock she also said they didnt break up he was in the army and had to move away she said 'my mum was really sorry when he left because she wanted us to have caramel babies'. She has two close friends who love black guys one only relaxs with black guys now and I know they talk about it when they are together. We have a great sex life and she is really open minded. She loves anal occasioanally and loves me going down on her and has really powerful orgasms when I do. I dont often make her cum during sex and although she says she is happy with my 6 inches there is definietely room for a lot more in her beautiful clean shaven pussy.
I am a little concerned about introducing the idea of her fucking another man as I am worried it will change the dynamics of the relationship and to be honest weird her out a bit. I have introduced the idea to one girlfriend previously. I first told her about it when we were out takeing and talking about fantasy's after we had been together about 1 year. She slowly took to the idea, we talked about it during sex and I wrote interracial stories for her, with her as the star. One night when we were in a hotel I organised a interracial cuckold presentation to her which she loved. She dressed up in the sexiest underwear and I gave her some stuff to read about it first then spoke to her and then showed her two videos while I went down on her. During the videos i said to her if there was a black man here right now with us would you fuck him and she said 'YES!!. We ran into relationship issues a little after that (nothing in relation to cuckolding) and split up.
I was planning to do a similar thing with my current girlfriend, although we have only been together 1 year it seems like it is really going to last she has talked about marriage and kids etc. I was wondering if anyone could give me any guidance or help on the best way to introduce the idea to her if you think repeating above is a good idea?
Also the best video(s) I can show her which might help to get her interested. I have been into interracial porn since my teens so I have watched a lot but I know what I like, which isnt nessecarily the best thing to try to get my beautiful girlfiend into it. If you could send me any links, maybe ones you have shown to your wives/girlfriends or maybe ones you wifes/girlfiends have really enjoyed or did the job for you I would be so grateful.
any help really will be gratefully received.
thank you!!