Only you know your wife...but this is similar to what I did. I knew it would be difficult for my wife to talk about the subject let alone bring it up on her own. I also stated that I wouldnt wait forever, but didnt put a definate time limit out there (ie 1 month).
The other thing I did was leave the kids out of it. I didnt say we should be together for the kids. I presented it as a strictly her and I thing. Both of us have been divorced before, both had kids from those marriages. Kids are strong and although not ideal, they can survive a divorce. So really, I kept it to why I wanted to be with her. I left out all of my good qualities cause when you read it back, it sounds like a used car pitch.