We too homeschool and my H was away from home 220 nights a year and the nights/days he was home he spent doing "his" thing, so the kids felt very left out.
We joined the y so we could swim or walk the track, or take a class when we felt the need for something more.
We too are very minimal homeschoolers, we do not do "field trips" everyday as some do, nor do the kids take tons of outside classes, they take what interests them and they HAVE to follow through so they make their choices wisely
In our case we got to liking dad being gone, it made life so much easier, so much less fuss, simpler meals, easier clean up, etc. That is not good, and not what you are going for, I know, but something he should be aware of, you and the kids are bonding in ways he has no idea about, he is very excluded from this bond (of his own choice, not saying you are purposefully doing it, it just happens, even if you try to "include" daddy, the kids wise up and they realize that what is important to a person is where they spend their time and they see where all dads time is spent, even if dad uses the "I am providing for you" line, they know the truth).
I say let dad answer any questions himself, if they want to know when he is getting home, let them call him then when he does not get home by x time he is the liar not you. Let him make plans with the kids for Saturday and let him deal with the fall out when he bails, that is not your job. Time goes by way too fast, your H needs some reality consequences now, not when the kids are grown and he looks back and then realizes what all he missed out on, cause there are no do overs in this area, when the time is gone, it never can come back.
I have one friend who travels M-F and he is a single dad with 8 kids, (only 5 are still in school, and the older three help out with the younger) but he has a date night every Saturday with one kid, just the two of them go out to dinner and chat, catch up, etc. Perhaps he could work on some of that one on one time with them (and he only has two to divide his time by )
Also, having his own business, perhaps he needs an employee or another employee so he can have more family time?
congrats on your "talk" last night, I hope it goes to the heart.