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The are about the same peak HP to peak HP (torque totally different but that's not important in the manner people like to argue) The 250f also has a 3000-4000 LARGER window of usable power range and 5000-6000 higher rpm limit which helps with final drive gearing/mechanical advantage In fact - in many recent tests of mine - the 250f's will out drag race a 250 two stroke japanese bike stock to stock. The KTM 250sx being an exception to that - while MXA is reporting it maybe worse for 2019 - my dyno is reporting it to be stupidly...

A quick Google search turns up several options for rentals in SoCal. I do not have experience with any of them, but it might be worth an e-mail or phone call.

I probably wouldn't bank on some random moto dad loaning you his kid's bike but surely there are people on moto boards like this one that would loan you a bike, pre-arranged so you don't have to worry about whether or not your son will get a ride.

Bro, before you try to buy/sell a bike like that, just go to the track, walk up to some Dad and tell him your story. I Can't imagine that people would not share their kids bike with your son. I know I'd be stoked to do it. Motofamilies will usually give the shirt off their back when there's a young kid trying to ride.

Most of the SoCal tracks have kids tracks, and even the Vet tracks i consider kids tracks and make it easy for you to ride with your child. Just be careful on the weekends

Most of the tracks in socal have a separate kids track lacr perris pala milestone comp edge.

One word. Insurance

The DT1 track in Tulare, CA splits up the riding sessions. Fast, slow and kids. At the end of the day when there are very few riders they'll often combine everyone. There's also a vet/kids track that stays open all the time. No jumps to speak of on that one, you'll see kids rolling around it for hours on end.

I cant speak for the California tracks, but most tracks around here have kids specific tracks. The ones that dont will/should have split practice times so kids arent out there with 450D riders. Here in Georgia both Highland Park and Durhamtown have rental bikes. Unfortunately the only kids bikes they have are trail bikes.

I have no help in the subject. But that sounds like a fantastic time and way to make ever lasting memories.

2 words for you.....Do it!!! Don't think about it, don't hesitate, don't have any doubts, just do it! The amazing time you will have with your son will create even more amazing memories not just for you, but for your son as well. Memories that will last your's and his lifetime. I have spent a lot of time over the years riding in America. And each and every time there has always been plenty of kids riding at all the SoCal tracks. If I was you I wouldn't worry about pulling down his bike and putting it in a suitcase...

You can buy a bike and put it on consignment when done. Pay like a % fee if the sale price for them advertising it on their floor. Definitely do it.