i have strong opinions about this, too. stay away from the 410, it's an expert's gun, go with a 28 or 20. i have 7 year old who regulary breaks skeet targets on a regulation skeet field with a n.e.f. single shot 28. it does not recoil toomuch and has about the best pattern in shotguns. not necessarily the n.e.f., but the 28. we have a express 870 youth 20 ga, it kicks way to much for a small kid, it is not fun to shoot for my 11 year old, and she's 5'7" and 160, been shooting since she was 3, with help of course. she has a beretta 390 youth in drool paint she just loves to shoot.
the 28 is more expensive in ammo, but , it kicks less than a 20 and has just about the same effective pattern. the 410 has about a 6" smaller, in diameter, effective pattern for a given choke.
i shot competitively for a long time, it just seems to work better for a kid if they start with a gun they can hold by themselves and hit targets with. the confidence factor is very important. a little money spent on gun fit every year goes along way towards relieving the recoil and the problems that stem from it. keep the kid in a gun that fits them will really help them. they will not want to lift thier head to get away from the recoil, they will have confidence from breaking more targets, you will both have alot more fun.