If you don't mind a bit of a drive, Saturday nights, K3 (Kankakee, IL) gets more champ karts than any track in the midwest. They get a good group of jr 1 champs every week. They run baby champs, jr1 (purple plate flathead) champs, jr 2 (blue plate flathead), jr unrestricted (unrestricted flathead), and sr champ (unrestricted flathead and 3 hole gold animal) weekly. Lake Village in northwestern IN is also running champs on Sundays, so you could make a weekend of it.
We have a group of kids running purple plate flat heads (Jr Champs) at lil eldora.
265#. There were 5 of them there for the first race. All beginners. Information on ages and weight should be on their website.