Agree with all the points above, key things for me with two girls (6yo enjoys cycling has good frog bike is quite short for her age, and 4yo who won't really entertain the idea)...
- Let them choose - I found this hard until recently, often "forcing" them to do more than they wanted to. We recently went to the Tissington Trail in Derbyshire, a nice flat ex-Railway track, and gave the 6yo the option of a short ride on her own bike or a long ride in the trailer - she chose trailer this time
but said at the end she wanted her own bike next time! - The right route - especially with the smaller bikes, any small hills seem much harder! We live near a reservoir with an 8 mile route round it... in theory nice and flat, in reality lots of short and sharp ups & downs which sapped the 6yo's energy
