Well I actually sent my doctor an e-mail and although he takes a while to reply he did answer my question. He said enema / colonic are very common practice and are not dangerous if done properly. He said there is no scientific research or studies showing that coffee is better then saline solution, but coffee in it's own is a stimulant that will help you release more. That's why you typically need to go after drinking a couple of cups of coffee. This is probably the reason why it was added to the common enema as you will release more with coffee.
He suggested using disposable applicators and trying one without coffee first then give it a week and try it again with a small amount of coffee. Since I drink coffee daily he didn't think I would have any problems handling the caffeine rush. He suggested not doing them daily or weekly, but bi-weekly as toxins won't build up that fast.
With that said I'm going to go for it!! I just need to find a way to convenience my girlfriend to hold the shaft and make sure to stop the flow if things go south!!