Yes it is possible.
This article should help you with configuring the router optimally: http://support.apple.com/kb/ht4199
Also, here's a link with some more info about iOS devices and dual band: http://arstechnica.com/apple/2012/11/best-of-both-worlds-setting-up-wi-fi-for-io s-on-2-4-and-5ghz/
Hope these links help; please reply with any questions.
Thanks for the info and links. I will check them out. So you say that my older IOS devices do support dual-band wi-fi. (I forgot to mention--one is running IOS7--the Ipad Mini. The Ipad 2 and Ipod Touch 4 are still on IOS6. (I could upgrade the Ipad 2 to ios7, but have not yet done it.)
It isn't only a matter of configuring the router though. That would matter for my home network, But I am also wondering about at work, at public hotspots, etc., where I have no control over the router? Is there any way of configuring the idevices themselves to get better performance? (I certainly have not yet seen a control of which band to use? Do they work better on the 5ghz band?) I assume they are N compatible, not likely AC.