We just did this on Thursday. My husband was approached by a CM. DH had DS 2 in a stroller while DS5 and I were on Spaceship Earth. The CMs hang out near the front of Epcot. I don't know how they choose. My husband thinks they either have a profile or they ask after a certain number of guests pass by.
After DS5 and I exited Spaceship Earth we met up with DH and DS2 and went to a Desk to the right of Spaceship Earth (to the right of the photo shop). We were asked what time we would like to start. They had about 8 slots for every 1/2 hour. We were able to get a 11;45-12:00 Spot. Most of the times were already filled in.
They asked us how many in our party will play the game. We only said 2 since DS2 is too young and DH volunteered to watch DS2 while DS5 and I played.
The CM's gave us a map of Epcot with a spot in Canada marked. We were to arrive at the hotel in Canada between 11:45 and 12:00. We were to look for the CM under the green umbrella. We had 12:00 Le Cellier reservations so they said we could pick up our "kimmunicators" and then go to lunch. We didn't have to start the game until after lunch. They said the game would take about 2 hours but we could play take as much time as we needed as long as we returned the Kimmunicators by 6:00 pm.
The CM's asked us our Secret agent names. DS5 couldn't think of anything so they asked him his favorite character. He became Agent Stitch and I was Agent Pooh Bear.
We then went on Soarin, Mission Space and Test Track. We were on Test track longer than expected, so we had to run to Canada. We arrived at 11:50. We had to leave a Credit Card on file in case we damaged or didn't return the kimmunicators. We saw a short movie about our mission and were given our kimmunicators.
The kimmunicators are cell phones that have a tracking device. I think so they know where you are, also they identify you at a certain point in the game (it's great when they identify you, but I don't want to give it away).
The kimmunicators had certain missions that you had to complete. Each time you completed a mission , a new mission would be downloaded. Our contries were France and UK. After completing the missions you went to the Imagination pavillion.
It was great fun. It took us 1 hour and 45 minutes after we had lunch. My Kimmunicator did mess up. It didn't upload a mission. I was able to turn it off for a minute and back on. This rebooted my phone. I did have to backtrack to France from the UK and that was a pain.
This was super fun.

My DS5 and I absolutely loved it. DS5 can't read yet, but they show pictures of the clues so he was able to find them. DS5 is usually a little bored in World Showcase, but he was occupied the whole 1 hour and 45 minutes. He learned a lot of interesting facts about France and UK with the help of characters from a loved show.
DH and DS2 came along with us for the whole mission. Good thing, I needed DH's help in finding some of the clues. Some of the clue sites did get a little clogged up with other agents. There were some kids that found out my name and saw me later and said, "look, there's Agent Pooh Bear". It was too cute.
If I were to do it again, I would just have DS5 get the Kimmunicator and help him. Since I had one that got stuck, it slowed things down. If you have kids 4 and up, they will probably want their own kimmunicators. DS2 had no problem not having one.
DS5 wanted to go again on Friday, but we had to talk him out of it. 2 hours is a big chunk of touring time. Oh yeah at one time we were approached by and undercover CM to make sure everything was okay. He was a tall good looking man in tourist clothing. If you get to go on this, you will have a blast!