Getting back into the sport



What's up everyone. So, I'm heavy on the fence about coming back. Been out of the game for about 10years. I rode advanced on a 600 for about 4 years and loved it. Life happened, got married, had kids all that good stuff. Now i've got a 6&8 yo that want to ride so I'm checking into the ovahles. They have been riding dirt since they were 3-4. So couple questions:
-can kids ride on track with the big bikes/or is there a kids class nowadays?
-I was 135 on my 600, I'm now 6'1 190 so should i get...

Getting back into the sport