RDD,
I cut down a used std. weight Remington 1100 20 ga for my daughter to learn to shoot with when she was quite young. Loaded 3/4oz light loads in it, but they would still cycle the action. Had another indivisual teach her initially on purpose so there was no intimidation .. he was a elderly skeet champ whom she really liked as a person and it only served to help reinforce good habits and the rules of gun safety .. and I am not an instructor nor a skeet champ. Long story short, I have several dif length stocks for that gun, the shortest is cut back to where the stock nut just clears enough to get the butt plate on it; it has a short plain bbl with a simple silver bead fitted with no choke whatsoever. It will break clay targets at amazing distances [trap or sporting clays] with std. quality target loads. Peter Blakely uses it today and has for many years to teach youngsters to shoot with. It will go to my grandson at some point as it was his mother's shotgun. Peter taught him to shoot with it some years ago when he was quite young.
As tempting as it is, I would strongly advise against the .410 in particular unless your daughters are going to use it shooting squirrel or rabbit [as in mostly stationary targets] and the 28 has no inherent advantage when a 20 can be loaded with 3/4oz loads and will as a rule be just as easy for them to shoot with the softer/light loads. There is also an advantage to using a gas gun from the recoil perspective. Muzzle blast can be as damaging as recoil to a new young shooter, so please don't overlook that aspect either.
These are just some thots, they paid good dividends for me. My daughter became a very good shot and the grandson is also. Neither had any problem transitioning to doubles later for targets or game.
Perhaps something of use to you, glad you are introducing them to the sport early and hope they both derive much pleasure from it and will carry it through their adult lives.
Kind regards,
tw
