One of the problems with a wide vagina is that the gal, herself, does not get the stimulation she needs. I believe it is up to the guy fucking her at the time to do whatever is necessary to give her sexual pleasure, and that his pleasure is secondary.
The best way to do that, with a gal who can't really feel your cock, is to eat her! You can find her clit with your tongue and lips and drive her to the heights of ecstacy.
The next question is: "How do I cum then?" The answer is that you masturbate while eating her pussy, and when you know she is about to cum, you time your orgasm to match with hers. Then while she is cumming, and pulling your face as deep into her cunt as she can, you are cumming too.
Now, I know that some guys will feel cheated if they don't get to cum in her pussy, so if you are one of those, simply jack-off until you're about to cum, then get into position between her legs and as you start to cum, shove your prick up into her hole and fill her with your cum.
I do realize there are some guys who consider it less than "macho" to have to rely on jacking-off to get pleasure when a lovely naked woman is there, and who might even be embarrassed for the lady to know that they masturbate. The sooner you both are able to get past this minor problem, the happier you will be.
I'll say it again: Your job as a lover is to give sexual pleasure to your woman.