What type of bike would an 8-10 year old need for a track like this?

I take my son to this track. He just moved on to the main track from the kiddie area. He can ride/roll on to the berm but no fancy jump yet. He really wants to shred like the big kids. We have a casual (Priority) kid bike and I notice the bottom of the frame would hit ground.

Should I get him a bmx? A dirt jumper? Do you need to front suspension for track like this? I noticed at the track. What is a good size for 8-10yr old? Thanks.