Flickr seem institutionally predisposed to making life as difficult as possible for users of iDevices
I think Flickr still aspires to be the ‘photographers’ medium and as such, regards camera phones with a certain amount of disdain, despite as you point out, them being the most popular devices with which Flickr images are created.
Instagram has stolen the lead from Flickr preicesely because of this; they’ve made their platform much more user friendly for camera phones but as a consequence, it’s a less serious platform for sharing ‘fine art’ photography.
OP if your club is anything other than a photography club (which I guess it is), I would think that Facebook is probably the best option. You’ll likely get more from sharing photographs if you focus on that being about community and community building rather than just about sharing images. Facebook is very good for that.
There are lots of other photo sharind sites like 500pix, Instagram, Smugmug, Dropbox etc, but none really come close to providing a sense of community around a club or society; they’re all more focused on sharing images.