i drank around the world in 2007 all by myself. i had no trouble whatsoever drinking 11 drinks in the 10 hours or so we were there. are you kidding? that's basically 1 drink an hour; that is nothing!

and we still managed to go on all the rides and see the shows. unfortunately, i didn't know anything about a passport at that time. i just took pictures of each drink, and yes i remembered every drink!

because i did spread the drinking out for the whole day, i never actually even got a buzz, but that's not why i was drinking around the world anyway. i am going back to epcot for f&w in october and will be attempting to drink around the world again. since there are more countries/kiosks (29 i think), i will probably share with my fiance this time (and he has even higher tolerance than i do!

).
ok, back to some of your questions. it cost about $100 to drink around the world in 2007. that's about $10 a drink. some of the mixed drinks were a little more than $10, while most of the beers were under $10. i also did shots at a few countries. that $100 is just for drinks. i didn't eat much during our jaunt, but i probably spent another $15-$20 on food (crepes were the most expensive food item i bought).
the size of the drinks varied depending on the type of drink. i would say the beers were no bigger than 12 oz. the shots were of course 1-2 oz. the mixed drink is where it varied. i had a drink in paris that was probably about 6 ounces??? the saki drinks were closer to 3-4 oz. since you're going with people and aren't sure how much you can handle, i would just share with your aunts/uncles/cousins.
keep in mind this was 5 years ago, so i have no idea how much has changed in that time. as some people already said, google search "drinking around the world," and you'll get a lot of good ideas. you can always make your own passport book to save money. i don't see why the CMs wouldn't sign/stamp a homemade one.
good luck!!
