I would look at Alliant Powder's website, in their reloading data, and also look at Hodgdon's data. It will widen your choices.
A word of caution ....... the little .410 usually runs at high pressures, and with the confined space in that hull, a very small mistake on a powder charge can be disastrous. Not trying to scare you, but simply making the point that you need to check your drops more often than you perhaps would with another gauge.
Try to find a load that agrees with your tastes, and has a lower pressure. Wad changes are usually the biggest factor on this hull. Same powder, same primer, different wad = wide pressure variations. I know you are a seasoned reloader, but I have to say it one more time .....
ESPECIALLY with the .410, don't substitute components unless you are ABSOLUTELY SURE of what you are doing and have data to back it up.
Be Safe .... and have FUN with your child! Don't let him get discouraged with the .410 ... it is referred to by the top skeet shooters as "The Expert's Gun" ... and for good reason.
EDIT: Oops ... forgot the load .... We usually favor H110 with a Win. 209 primer, and WAA410HS wad. At 16.3 grains of powder, it is only 9,300 PSI and runs about 1250fps or so. We seem to get better breaks at 1250 or better. I don't know your son's age or stature, but if you need to drop the load for whatever reason, you can back it down to 1200 and be fine. I think this load is listed on Hodgdon's website, along with several variations on the powder charge.