What is a reasonable expectation?

[5 Little Monkeys]

I agree, I don't think it's unreasonable! She may just need to get used to it though. Our walks are anywhere from 30-60 minutes (mind you this is sauntering along, stopping to play etc) but 20 minutes for a 4 year old is totally doable

[Lee-Bee]

As the others have said, not unreasonable but it will take time to get used to. Keep the pace slow and distract her by chatting. Does't help that it is winter and she is in extra layers.

Have fun!