Family across country road trip

Headed West wrote:
The DW and I decided 400 miles a day should be the max from now on for a relaxing day of driving.

Having done this many times I'd agree. Here in Canada we've been using the metric system for quite a few years now so I think in terms of ~ 600 kms (~ 375 miles) as about the most interstate driving I want to do in a day, while 400 kms (~ 250 miles) would be my max for 2 lane driving, especially if mountain grades are involved. Regardless, there were times when that 375 to 400 miles would land us where there's absolutely nothing around, less so in the east but not uncommon at all the further west one is, so an occasional longer day was inevitable no matter how well we planned. The OP hasn't indicated his exact departure point in Colorado but with Denver to OBX being about 1900 miles I'd want to allow at least 5 days out and 5 days back based on an overall trip average of 50 mph. That's a lotta driving just to get to the beach! :E