Did you notice how in the beginning Roy's team is just him, Hawkeye and Havoc. And after the timeskip Falman, Breda and Fuery joined?
I headcanon that the three were put into the team when Mustang was stationed to East City. And because of this the team had to learn to work together. Of course with them it was quick since they shared working space but Ed is travelling the country and just never has the time.
So it takes a few months until HR decides the team should spend a few days in training, like Special Ops style. Sleeping in tent, training missions and such, it would be a bit like bootcamp but the purpose was to hitch the team together.
Fuery and Breda, who have yet to meet Ed, are afraid the boy might be arrogant, he is a prodigy after all. Ed is worried they won't like him and will 'baby' him.
"Chief is fine, he will go from 0 to 100 in a millisecond but you'll like him" Havoc says.
Hughes tries to tell Ed that everyone is excited to meet him and to Fuery and Breda he says "the kid is all bark and no bite." He even offers to be a supervisor during this training.
And on the first morning Edward shows up in cargo pants, jacket, shoes and a shy smile and every adult in their head's vow to protect that child forever.
Some other notions, feel free to add:
- Ed has amazing survival skills, he outshines everyone. He can identify every fish they catch and make a fire using nothing but sticks
- Ed is also good with maps. Their training missions includes finding four pitchstops and he quickly becomes their main navigator
- Hughes advices others that the way to Ed's heart is to ask for the boy's help. Fuery takes this advice and includes Ed in his tasks and soon they are deep in talk
- Mustang has already suspected Ed can't swim due to his automail and gets confirmation when the boy absolutely refuses to go to the lake despite it being a scorching hot day. By the last day and after lots of convincing and promises to help if need arose the boy gathers enough courage and enters the lake
- Mustang is already planning deep water rescue training
- Ed is the first to crash at night, which is not too surprising, although he makes a valiant effort to stay awake and is pretty much sleeptalking by the end.