M.R.
From personal experience, I would say that a workaholic does not change on their own, unless you kindly point it out to them, in a language they understand and in concrete examples they will readily see.
Over the years I have planted seeds of time: that our children have only so many years at home before they leave for college, and that means XX number of summer vacations and spring breaks, and how would he like to spend them with his kids before they leave home? What sorts of vacations did he envision as a father?
What kind of family vacations would he look forward to? Totally relaxing by a beach with no interruption kinds, traveling 3rd world countries by catamaran, going on a European planned vacation where no one has to plan any details, a Disney cruise.....hopefully he'll start thinking about what types and how he wants to spend down time with his kids. It would be interesting to learn what he has in mind.
When I took this approach it turns out my husband wanted ski vacations with the kids, and it surprised me. We had never skiied. And once he voiced that, he went all out and took care of the ski equipment and ski passes, etc. I got the ski clothes.
This mathematical approach was really helpful to get my husband involved in knowing that our young family grows fast and we have a limited amount of family time to enjoy.
Even without a big vacation plan, it's important to plan the weekends with a few fun, relaxing activities. After only a few weekends of the kids and I going out with family / friends / clubs / sports, my husband wanted to be part of the joy, so he started to protect weekend time that he was able to.
So, with a lot of gentle questioning, and genuinely wanting to know what he would like to do, he has become comfortable voicing his opinion and knowing we'll listen and compromise.
There are definite cycles to the month I imagine for you husband's business. Perhaps you can protect a weekend that he can go in late, leave early, etc for a special trip. Hopefully with time he'll learn to prioritize a few big ticket items for the day and leave the rest for tomorrow.