I'm tiny so my fiance and I shared drinks and it worked out perfectly (more so - he drank all of the beer and I drank all of the cocktails). We did start in Mexico and ended in Canada but double backed to England for fish and chips while watching Illuminations. I would suggest to not rush your time! Go to the shops, explore the pavilion, take pictures (especially one with your drink in each country). Afterward, because Epcot closed at 9 that night, we walked to Fantasia Mini Golf and halfway through started to sober up. Was a wonderful day over all.
I wish I hadn't ordered the Canto Loopy from China. I read reviews for drinking around the world online and this was raved about. It was incredibly too sweet for me, and I love sweet drinks.
If money is tight, I would suggest specifically ordering without the souvenir cups - this does save you some money as you are not paying at the advertised price and is discounted a few dollars. Of course, this is only for those drinks that already say it comes in a souvenir cup.
Drink lots of water. Eat. Take your time. Take pictures. Have fun!