Mistress_C is so right. Once you let the cat out of the bag it is sometimes difficult, if not impossible to put it back in it! All women have at one time or another fatasized about group sex with more than one man, or even with someone other than their spouse. I can perfectly understand your desire and passion to let this thing happen, (we've all been through it and it IS a very cosuming desire) but keep in mind that later down the road it may be totally out of your control.
Many guys who have started like you have ended up unhappy or even divorced. Be absolutlely sure you want to be a cuckold husband before you entice her enough to make you one. Once she does and decides she enjoys her bull more than you it will be too late to pull the reigns in on her an you will either have to live with it or move on. She will be the one in control and you will take it and like it like a good little cuckold, or else you will have to start all over with someone else.
Just words of caution. If you really decide you want it to happen above all else, you should be presenting her with opportunities rather than just pushing her. A few takes while she is left alone with a ptential bull guy "friend" while you go to the store for more cuckold water, and then be sure you can look in through a window before returning. Take your time. You might be pleasantly surprised upon returning to find that she's taken you up on your offer and has seized the golden opportunity to cukcold you with the guy.
Good luck and enjoy! Most of us do!
That's a picture of me each time it happens with my wife!!