Are my kids too big for a pw 50?

Nope. Probably a bigger KTM 50. My son was 4-5yrs old at 40lbs when he was on a pw50
You may want to even consider a 65

Look at the honda 110 very beginner friendly bike. Or a TTR. A KTM 65 is no joke

If it were me and my kids were that size and just starting I would look at a Yamaha ttr-90 or a Honda 70. Both bigger in size and much easier to manage than a KTM 50 or any brand 65.

The best alternative to the pw50 for your kids age is the Honda crf50 or the Yamaha ttr50. These are not race bikes, but rather fun bikes. Perfect for a beginner. Makes sense for a couple of reasons. One is that they are older and smarter and can handle the three gears, but you can also just put it in second and let them ride all day. The second is that they have a slightly taller seat Height and your kids will be growing. Finally, you can modify these bikes as the kids grow, and they can be play bikes forever.

You might also check out the crf70/110

CRF 70

this all day

my daughter started on a PW50, then we got her a 70 and now she is on a 100

DO NOT get a beginner 8 year old a 65 or 85 2 stroke!!

My first bike was a KX65 at age 8. It scared the piss out of me staring at it in the garage, let alone kicking it over for the first time but man was it thrilling.

Learned how to operate a clutch on that bike and it was the first thing I raced as well. My brother was 11 when we first got it and by the time we were comfortable on it and ready to race, he was already to old and needed an 85 if he wanted to. Luckily for me that meant it was all mine at that point!

If you plan on getting them into racing or at least riding the bike for more than a year, get a 65. I'm just afraid they'll outgrow it very fast. I couldn't imagine having as much fun on the track as I did on the 65 when I was that age.

If you don't plan on racing, I'd still et something bigger than a PW50.

I learned a clutch at about that age along with all my daughters. XR80 clutch is butter. They can basically dump it and the bike will take off just fine. Much better bike than the 70.

Do they still make PW80's ? They're bulletproof, with 3 speed automatics so they can learn about shifting without stalling. Low seat height and easy to ride. Our theory on kids on bikes was just make sure they have fun. A smaller bike they can ride the wheels off of is going to be more fun to ride than something a little too big and heavy for them. Whatever you wind up with let them stay on it until they can ride the piss out of it, so what if it blows up and they flatten the rims overjumping it, let them feel like hero's ringing the shit out of it and throwing it around. They have their whole lives to go fast and be serious. Just my $.02

A semi-auto 110(CRF/KLX) would be a perfect fit And after they learned the basics of riding, go on to a KTM 65SX.

KLX110 with the auto clutch has been great for us. Perfect beginner bike for that age and Dad can rip around on it too. I'm sure the Honda / Yamaha equivalent is great as well. Just look for a deal and a good dealer.

The PW 50 is too small. 50/65 racing bikes are too violent for beginners. So PW80, CRF70 etc are good to go.

You can also ask a shop or a mechanic to build a "plastic brid" (I do not know the english name) to block the throttle at max 50% then 75% (if going for a 2 stroke, where most of the power is). That can help them not to be scared about it, and also make the transition rapidly to a 85 once they are about 5' (in about 1 1/2 years).