Shifter Karts will give you an adrenalin fix. Relatively cheap “fast” fun, Like M/C road racing (chassis / gearing / jetting) to develop / optimize as you work to get to your best. BTW spec tires are not cheap !
One is a Heroic youth XL (I believe). (Paid $750) https://www.heroicracing.com/HEROIC-GENESIS-CHILDREN-S-ROAD-RACING-SUIT-p/hrarscgenc.htm The second is a Furygan size 12 I got from Chris Ulrich....Alex wore it exactly once. (Paid $350) The other suit is a HistoricGP suit we had done for him custom. We got his measurements in right before the Summer growth spurt kicked in and it was snug when he got it. Wore it 3 or 4 times (one crash) and now he's done with it. ($paid 550) All of them have a little rashing on them...none have any stitching damage of any kind. Going to wait as long as possible to get him a new suit for 2022. And I think he's got his fingers crossed that Dad will get him the new youth Dianese suit. So, IF I can sell these 3 to help pay for that new one, bonus.
The outright lap record at Cadwell Park is held by a kart, nearly 5 seconds faster than the bike one. Even going back to 1970's when I first went there Karts have always been the fastest vehicle around that track.
Get on Youtube and look up some videos on electric karts. Wicked fast with almost no maintenance. I'm not a fan of the whole electric car dealio but for a racing kart application it is pretty damn cool.
My take is that if your kid's really going to run his kart around the neighborhood it needs to be a caged rec kart. Not because he's going to get it upside down, but because of all the things he could potentially run it under. Pickup bumper, picnic table, chain link fence, etc.
Any motorized vehicle not designed to be driven on public roadways is probably not a great idea. Full disclosure, I lead my daughters on parade laps on their dirt bikes within my neighborhood but if you're not going to be monitoring him full time, setting a pre-pubescent boy loose on public roads with a go kart is asking/begging for trouble. [EDIT: but, in typical BBS fashion if you eschew this advice and already know you're going to get him a kart, go electric. To your point in the OP, it's just soooooooo much easier.]
another option is an e-kart league for kids and adults. Around here we have 8 week seasons and its $350 for early signup. I would consult Josh Owen on how to handle the celebrity status that comes with E championships
I know of a cart for sale in the north Atlanta suburbs. Not mine. Teen-age grandson of a friend of mine.
I was a long time karter, mostly fast stuff like unlimited 2 cycle and various 125cc shifter karts. Driving anything more than a 3hp lawn kart on the street is far more risky than on a proper track. I like the idea of indoor kart league for the kid or you. If you want to buy something then go to the track where you want to race, ask questions then buy used from a local racer and have him help you at your first outing. Good Luck and have fun!
How about one of these: http://www.go-bowen.com/product/dirt_bike/go-kart.html I'm going to look at one tomorrow that's used, 48 volts should move out pretty good. (Xmas present for my 5 year old boy.) I'd go electric to minimize the noise also.
https://www.redfoxpowersports.com/200-gvs-200-cc-kid-size-go-kart-spare-wheel I got my kids (8yo & 6yo) a couple of these when we moved on to our 10acre place earlier this year. My son rolled his already, so as mentioned getting something with a cage and nets is a good idea. I had to add the nets to them separately. we cut them a .34 mile track in the prairie grass. They loved it and were having a blast til he rolled it. Now their a little shy about them, but I’m hoping they’ll warm back up to it.
They both have MX650 Razor dirt bikes. The girl uses hers the most. The boy not so much as the other kids don't, so he rides his bike or scooter so they can stay together :\ wonder how much is that? This is a great idea, and considering we get winter up here. It already started though, 12 weeks/$600. They advertise $75/week, hopefully they have a spot for the few weeks that are left.
They're not cheap new, around $1000 IIRC. Used, I've seen them for $600ish. The one I'm looking at is $200 but will need new batteries, as they all do. (Think any Razor or Power Wheels product) Four 12 volt batteries is only $80 though so not bad at all. May even bump to 60 volts down the road. Best thing about this one is the brushless motor. Infinitely better than conventional brushed motors.