yes, the gold-coloured 12-siders were a very distictive coin - but they weren't called joeys - that was purely for the little round silver ones - which co-existed with the 12 siders for many years.
And you are quite correct about the shilling and two shilling pieces continuing in used post-decimalisation. Can't remember perzacly when they went out - I think it was before they introduced the new, smaller 5p and 10p coins, but I ain't sure.
The sixpence-piece continued after decimalisation for a while - probably until they withdrew the ½p coin (6d = 2½p)