micro gearing standard is 25:9 and I guess 27:10. Most cheaper bmxs dont have micro gearing. The goose has a 33 t front ring so im guessing its 12 on the back.
The obsession with micro gearing is all fashion driven. Yes it does give more clearance if you drop into a vert at 90 degrees to it. And you do save a little weight. but seriously are your kids gonna even go anywhere near a vert ?
Ask matt hoffman if he needed micro gearing back 10 years back?
If you get them a bike with standard gearing it can be upgraded. but that involves a new wheel to as a 33 12 will most probably be running a freewheel and a 9t rear is sprocket /cassette type body .