Not too sure how far DS's pre-school is but it takes us 25 mins to get there via dropping DD off at school. I walk, he scoots so must be about 2 miles (I can check tomorrow if you want?) He has a Mini Micro scooter which is so well designed that it is really easy to push him if he gets too tired. The usual problem is me keeping up with him though
I often pick him up in the car though - partly because we have other things on later and need to get home and partly because it gives me another 5-10 mins to MN do stuff.
He then scooters on school run to pick up DD which is another 20 mins or so. He's 3.10 but has done it for over a year.
If he gets used to it, he'll be able to do it. A friend walked to and from KG with her 3 year old everyday and then back again in the afternoon to collect her eldest from school and that was about 2 miles. Quite often her 1.5 year old walked most of the way as well. Just think how fit he'll be and how well he will sleep at night (hopefully).
are there hills? at same age DS as you, our preschool run used to be 1.5 miles VERY hilly, So I cycled and towed him in trailer. a flatter 1.5 mile each way route he could cycle or scoot no problem. when he cycled (2 wheel pedal bike) I had to cycle with him to keep up.
There's a hill at the beginning and then it's all flat.
It's the safety thing I worry about on his bike. It's a 40 mile an hour road with big lorries using it. Even if he cycles on the pavement I have visions of him careering into the path of a 50tn jugganaught. Although that probably says more about my paranoia than his safety .
DS2 can go in the seat on the back of my bike - can you manage a bike seat AND a trailer?