She already mentioned bbc, that is great. When discussing buying a sex toy my girl (early in the relationship) jokingly mentioned a black dildo. Year later I bought her one. 10.5 inch, a bit softer which she loves. At first she was shocked by it's size. I didn't tell her anything in advance the day we finally used it, we had an incredible passionate sex for about an hour and then as we did reversed 69 I pulled it from under the sheets. She was incredibly wet from the sex we were having so I didn't have to use much lube on the dildo. I whispered she's going to receive a surprise. I started very slowly, teasing her at first. Few minutes in and she was able to take most of the lenght. Then I placed her on her back, raised her legs up and started to fuck her harder. I never heard her moaning and screaming like that. She was a bit embarrassed and thought I would be jealous. I reassured her I love it and we started to use it regularly. Couple of months ago I confessed I would love to watch her with a black guy. She was really surprised but excited at the same time. We agreed we will do it on our next vacation. I still have to tell her I need him to cum inside her as that is my ultimate fantasy.
Long story short, black dildo is a great start if you want to see your wife with a black guy one day. I am not there yet, but very close. Don't be concerned whether she'll like it or not, she most definitely will. My girl is the last person you'd suspect would enjoy a bbc, she's very thin and petite (5'3, 100lbs) but loves it every time.