But it's not just the three hours, is it? It's going to potentially impact the structure of the whole day, the timings of everything. And if the DCs want this arrangement so that they can have a drink (as a PP suggested) then that means the DH can't. So apart from maybe the evening, in effect the rest of the day is going to be about them, even if they're not there.
Exactly. The person I know who relies on her parents for lifts and school drop-offs and pick-ups probably thinks that it's only half an hour out of their day, but it's the restriction on what you can plan for the whole day (you can never arrange any full-day trips/jobs/errands) and, as you say, it means no alcohol, should you have otherwise wanted to have a glass of wine or a pint. Everything you might want to do on the day has to pass the 'will I be finished by the time they want to leave' test.
Whoever suggested DH may be absolutely exhausted and fall asleep after a 3 hour drive shock, unless he's in his 80s/90s, I don't think many people would find that too strenuous!
Plenty of older folk, not to mention those with disabilities, do find driving tiring - and not just those over 80 (a great many of whom no longer drive at all). I know it's a MN trope that driving for 3, 4, 5, 6+ hours is no different from a 2-mile trip to the supermarket, but irl, it's a long time to have to concentrate fully and it is often tiring. I know you can have regular stops, but of course, the more of those you have, the longer the journey takes you.
In fact, it's not unknown for men people of a certain age to have an afternoon snooze on Christmas Day, without any driving, with all the buzz of the day itself and the busy build up, along with a huge meal. I suppose that may partly be down to the booze, which he won't have an option to partake of this year.