We had a go at fixing things through Relate - it didn't work because my ex had already set up a relationship elsewhere, but I'm confident that if both parties were remotely interested in fixing the marriage, it would have provided a way to do that.
If they are likely to agree on property/money issues, and who gets the kids with what visiting rights, then a quickie divorce might well work. If you go for a no-fault divorce, then I think some degree of mediation is a required part of the process.
My divorce turned out not to be terribly amicable - he wanted his 50% NOW, at the cost of turfing our disabled daughter out of the house with no fallback - and I found a solicitor was tremendously helpful, brokering an arrangement that let me keep the house and pay him off over 2 years.
I learnt that 33 years of love and trust were irrelevant once love had died. On his part. Overnight, it seemed, I wasn't negotiating with someone who wanted the best for both of us, or the children, but only for himself. I'm very glad I went down the solicitor route, because I would not have beleived the change was possible until it happened.