Keep a pack of spare plugs (properly gapped) in the tool case. Also the spark plug wrench.
Treat the fuel
Look the belts over for cracking and chipping.
Check the bottoms of the skis for wear.
I think that is a liquid cooled model, so make sure the coolant is fresh, the correct type, and up to the worst case local temps.
If you are going to deal with altitude changes adjustments to the jets/carb. may be necessary.
Set up an obstacle course so the kids can learn how to handle the thing. Careful they can be scary dangerous.
Have fun!