I'd suggest the Gen4 in your case. Small hands will benefit from the smaller Gen4 grip, and part of the price difference is offset by the fact that you get 3 magazines with the full- and mid-size Gen4 Glocks, vs. only two mags with the Gen3s. Gen4 Glocks in .40 work just fine, and the dual-spring setup does make a small difference in reducing muzzle flip (I shot Gen3 and Gen4 G22 models side-by-side with the same ammo, over and over again, and I could see/feel a minor reduction in flip; whether you or I could take advantage of a difference this small is another question entirely).
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)