OK my wife or I have biked our 7.5 yr old to her new camp from Sunday (orientation) through today except for Tuesday. Sunday she didn't want to interrupt her day off, complained, foot-dragged, whined, refused to shift out of 1st gear and it took 20 min to go 1.6 miles. Each day had a measurable improvement in her performance from the previous day (holding a line, mostly but also familiarity w/ a new set of intersections), and other than the whiny day she was taking just about 15 minutes for the ride. She's been riding in the street more and more of the way, up through last night coming home in the bike lane of a few block section of a 4 lane road. She really wants to cross the 4-lane road and ride the bike lane out in the mornings too but that is something we don't even let her almost 11 yr old brother do yet.
But anyway, we have been comfortable w/ the 15 minute ride but today she powered through in 12 minutes, and she conked out as soon as she entered the parking lot to the tune of me needing to coax her the last few dozen yards to the bike rack. So hopefully next week will bring fitness increases. By the end of the summer it would be nice if she can lug her bike up over the curb to get it to the bike rack.