Planning a drive that works for grandparents and kids alike.
Build more frequent stops into the schedule than you would for a trip with just adults, since bathroom breaks, stretching, and meals matter more across a wider age range. A larger or more comfortable rental vehicle is often worth the extra cost for a multi-day drive with a bigger group.
Loop in everyone on the general plan ahead of time so expectations about pace and stops are aligned before day one. Building in a genuinely restful stop midway through a long multi-day drive tends to matter more than shaving an hour off drive time.