Hmmmm... As a teacher who likes taking kids on excursions and justifying them, how do any of these sound?

Well they could be practicing their mapping skills by helping to plan the route to take and directing you along the way.
There is definitely lots of number practice that could occur by calculating how much further it is until the next stop/destination/town and working out how long it will take to arrive based on travelling speed.
They could be practicing their budgeting and money skills by helping to plan the expenses for the trip and trying to stay within budget.
There's definitely some sort of geography and possibly even history skills to be learnt (if you do a bit of sightseeing)
There's definitely gross motor skills to be learnt
There's also social skills and being a graceful winner/loser during the actual competition.
They could practice their recount skills by verbally (or written if you want) recalling the events of the day(s). If they choose to write you've got lots of literacy skills involved

Hope these ideas help.