This is similar to what Darko Savic suggested, just a more permanent option. Instead of looking for short projects family members can work on together, the whole family could start a business (or the other members could join the workaholic on whatever they are already doing) and collaborate to keep it going and successful. Hopefully, professional collaboration would strengthen their personal relationships as well.
I understand that the issue is making all the members equally interested (or at least interested enough) in the business. So the person who is a workaholic and realizes that should start thinking about this in advance, preferably before going into a serious relationship with someone. But of course, it could be attempted later as well.
I think the main thing is to find common business interests with your partner, there are quite many couples who have a common business, having a shared professional activity often strengthens the relationship and therefore such relationships can last longer.
When it comes to kids, even if they are not very interested in what their parents are doing for a living, it's good to have a spare source of income you can always come back to, no need to always look for jobs, you feel more secured about your future.
Also, when both parents engage in the same professional activity there's a bigger chance that a kid will get interested in it too because the relationship with one parent is usually slightly or significantly better than with the other and it's easier to "inherit" interests from a person with whom you have a better relationship. In other words - if a father didn't get you interested in the family business, maybe a mom would.