Hello Pozoutdoors, I would not reccomend the Lyman slug mold for 20 ga.
Get your kids started on a Lee mold for .575" RB loads of 290 gr in a Commander wad, very accurate and deadly and will not kick like a mule.
Here you can use CSD wads and let the fun begin:
all your choices are here with CSD wad and how you trim them for fit
Cook your own home made slugs for pennies a load
Hoping it helps you.
Warmest regards,
PreciousVideoMemories