Are there any ways to adjust the speed of a 1/8 scale buggy say if my kid wanted to run it for a bit? So I could slow it way down?

On your radio, bring down the Throttle End Point Adjustment (EPA) to where you feel confident your kid could handle.

40%-60% perhaps?

What is the minimum level radio I would need to be able to do that? Haven't ordered my radio yet. Do those radiolink handle that or higher priced?

I could be wrong but i think most modern radio system these days come with these basic adjustments.

Dual rate, end point adjustments and trim are usually included but be sure to double check it before you buy your new radio.

Like i said, i could be wrong