All products can be giving to Apple for free for recycling and most recent ones can be traded in for a gift card. You're suggesting giving money instead of gift cards which is not a bad idea. I mean, I can see why they're not doing that, but it could definitely have an impact. Still, they're on the right track.
https://www.apple.com/environment/
This would be amazing.
The iPad mini 1 and iPad 2 are quite slow, I think technology moves too fast too be able to use products like that for such a long time. You could upgrade existing iPads with new chips for school or something similar like that, but again, that would cost them too much money.
Apple is still a company with shareholders and it has to live up to their expectations. As long as their business model is solid though, all other elements can be improved for sustainability. Cradle-to-cradle products, renewable energy, packaging, recycling; what they've been doing for the last few years has a big impact already. Wouldn't call it "falling well short".