Winchester makes a 1 oz load with 5 or 6 shot. Get an appropriate choke AND pattern test it. You should be good to 25 or 30 yds. Any further and TSS or some type of heavier than lead load would be appropriate.
I m assuming since you re talking low recoil, subgauge thst your son is young thus getting a Tom close is important anyway as he s in-experienced.
Good luck