This is not a standard offer. I found this out because the people there are nice.
Please be nice to them, whether they can accomodate you or not. :) There aren't many places in Australia, that'll give out free chocolate samples when they can.
Plan to have a special occassion where you get together a group (eg birthday, friends, introducing some people to Haighs chocolates …).
Contact your Haighs store, let them know what you are planning and ask them if they are able to do tours perhaps with a complimentary tasting along the way.
If they can do this, check what numbers they prefer to accommodate and when would be good (keep an eye out to avoid public holidays, and not too close to opening or closing time).
Make a group according to how many the shop can accommodate and when the time will be.
Get group together and enjoy chocolate. :)
Haighs tends on the sweeter side of chocolate.
I did this for a friend's birthday and plan to ask them again when I have family visiting from overseas :)
I'm not sure they offer the tour for children.
My group were adults in their 30's.