I want to try group dreaming in a lucid dream, but I’m very skeptical about it. I saw online that you have to come up with some kind of meeting spot and, if both dreamers go to sleep at the same time with the same REM stages, they can both find each other. This seems just too easy. . .somehow, I don’t think it will work like that. I’m inclined to say that group dreaming doesn’t exist, but I thought that I might give it a shot if people on here and scientific evidence or personal experiences that could help me understand how group dreaming works. I think it would be very cool if group dreaming was real.
This is a topic that is being experimented on in many dreaming groups, and your feeling seems to be right: It isn’t that easy. Dreams take place inside your own head.
It is more or less well known that human minds can have some degree of shared thoughts, feelings or subconscious activity. People can suddenly think of each other at the same time. Close family members can register each other’s pain. This seems to lie very deep in the subconscious mind, and I still haven’t met anyone who can do this at will.
This isn’t saying that group dreaming has no value. It is possible to make yourself dream about the same thing or theme as somebody else. This is called dream incubation. You just agree on the “prompt” and focus on it when you become lucid. It can be very interesting to compare your dreams afterwards!
P.S. I don’t have any scientific sources for my reply. It is just based on experience from several different dreaming groups and forums. 
I had a very eerie and memorable dream once related to bed sheets behaving paranormally over 10 years ago. I was sleeping in a bunk bed with one of my (then) best friends, and when I told him, he responded he had the same dream. I am a scientifically minded person, but if his claim is true then I have no idea what’s going on. EIther he was exaggerating, or perhaps some faint connection was established via brain waves? 
Anyway, group dreaming would be awesome if it were provably real. From time to time, I do have false LDs where I think I am sharing a dream with friends, and then it is always so cool to show off my powers or go on adventurous missions.
I once dreamt of an ice dragon, and the same night my significant other had a dream that a frozen solid station wagon rolled into the parking lot of her work.