Another option; take the Lynx bus. Busstop is right outside of DTD and at the TTC (but does add about 30 minutes when using that stop). If I'm not mistaken it's the 111. No transfer needed, adult price of $2,- each way. The bus stops right outside the parking area of the Florida Mall. And yes indeed; there is an M&M shop inside the FM. It's pretty central, can not miss it. If you haven't done so already; go to the homepage of FM and you'll find a list of all of the stores. Depending on the stores you want to visit and what you're planning on with the M&M shop, you might want to hit the guest services of FM first located in the center of the mall. When asking, they'll give you a booklet of all kinds of coupons for many of the stores. Up until at least last december there were coupons in there for the M&M store. Don't remember the littlest details but can remember something about an amount off when buying for a minimum set amount.
I regularly use Lynx while down at WDW, amongst others to the FM. Might be a tad bit biast seeing how we don't have accessible public transport in our neck of the wood
but have to say I love them, esp. when staying at SSR.