Near Wantirna, you could go to Alternate Worlds in Ringwood (a suburb or two north) or their Bayswater store (a suburb or so east). Check their website for details
http://www.alternateworlds.com.au/

Near Dingley? None I'm aware of.

If you want to shop generally Knox shopping centre is in Wantirna (has Myer, Kmart, Target, TRU). Southland shopping center is a bus ride west of Dingley (and has all the major chains Myer, David Jones, Target, Big W, Kmart, Toyworld, just no TRU) and my old local, Parkmore shopping centre is a couple of suburbs east (but it's small, Big W and Kmart only).

Hope this helps.