Hi Jennanymph,
I am going to share my thoughts perhaps more deeply and broadly (pun intended) than perhaps you intended or expected. If any of it is useful, great. If not, it did not cost anything.
As a straight man who loves receiving anal play and has been active solo for 40+ years, and with my wife playing with me for about 10 years (and me penetrating her for much less time, but AO), my response to such a question would be “is right now too soon?” 
However, I am surely an outlier. I have no idea how straight men in general feel about it. Heck, there are gay men who don’t like anal sex (being gay is about who you are attracted to, not necessarily how you do sex).
In the same way, straight women have a wide range of feelings and opinions on the subject.
My opinion is: Life is far too short and unpredictable to miss out (because you are worrying about what somebody else may feel about the subject) on potential opportunities that you would like to explore. My mantra is: If the conversation (or whatever) is going to happen eventually, it might as well happen right now!
One of Goethe’s couplets applies: “Whatever you can do or dream you can, begin it. Boldness has genius, power and magic in it. Until one is committed, there is hesitancy, the chance to draw back — concerning all acts of initiative (and creation), there is one elementary truth that ignorance of which kills countless ideas and splendid plans: that the moment one definitely commits oneself, then Providence moves too. All sorts of things occur to help one that would never otherwise have occurred. A whole stream of events issues from the decision, raising in one’s favor all manner of unforeseen incidents and meetings and material assistance, which no man could have dreamed would have come his way. Whatever you can do, or dream you can do, begin it. Boldness has genius, power, and magic in it. Begin it now.” [The attribution to Goethe has been questioned.]
I live by this statement. It’s a long story, but the moment I first read that statement, the obvious truth of it instantly altered my life and I stopped wasting time worrying about decisions, etc. I first saw this in the form of a fantastic, large piece of calligraphy artwork hanging in the central entry area of a large public library. I was so taken by it that I tracked down the artist, who convinced the current owner, who had loaned it to the library, to sell it back to the artist, who then sold it to me. I was not going to accept “no” as an answer.
I would say don’t focus on your partner and him exploring his own anus. Don’t be doubtful. Assume that your partner will want to participate in what you would like to be done to you, and that your partner just had not been sure how to ask you!!! Perhaps your partner may need to be “brought along” if your partner is not experienced with anal activities, but that could be extra fun. You presenting the subject with that kind of intent and energy will likely affect the outcome positively.
None of this needs to involve the subject of your partner experimenting with anal penetration of your partner. IMHO, that is just a complicating factor at this stage in things. Your partner may be thrilled to penetrate you, but might have different or varied or complicated feelings about their own anus. If their experience with you is positive for them, then they may decide to experiment with their own anus – and you can certainly (when the time is right) mention that you would enjoy playing with your partner if your partner would like to experiment. (When the time comes, try this: “Honey, I have read – I think it was in Cosmo – that some men have super-intense and extended orgasms while receiving anal play from their female partners…”) [Don’t say it, SELL it.]
I would not even mention your prior bad experience. That just brings up possible negatives into the conversation. You already know that the cause of the bad experience was “we were stupid” (probably too fast, not enough lube, not taking it in gentle stages over a period of several times, did not start with a very small butt plug, etc.).
Instead I suggest that you tell your partner the simple and direct truth: What you would like to experiment with – and present it to your partner as an opportunity!
How about this potential script…
“Hi Honey, I have been feeling like I really would like to experiment with anal sex. I have had only a tiny bit of experience with anal sex, so I know we would have to start slowly and carefully. I would be the “driver” and I would guide how quickly we proceed, so that you don’t need to be concerned about my comfort. This is something I would really like to try doing. I know it may take some practice and time, but I trust you and I trust you to listen to me guide us as we experiment. I have heard that most guys at least think they would like to have anal sex with their woman, but for whatever reason, they are afraid to ask about it or they have had bad experiences with the woman rejecting the idea. Well, here I am and I WANT to try it.”
I sincerely hope that you get what you want and enjoy both the process stress-free and the activity more than you ever dreamed was possible. And, with luck, your partner may discover new joys as well.
BE BOLD!
