1800 miles in 3 days with 3 kids in a truck. Crazy or not

Go with 8 days driving and 8 days in YS should be plenty. Actually during the 4 day drive if you can get someplace interesting and spend 2 nights to see something and get a break from driving that would be even better. Might cut your YS down a few more days but honestly 4 to 6 days in YS is probably enough. The trip will be far more relaxed and enjoyed by all.

Or do you really have 10 full days of activities in YS planned out?

JMHO