Sometimes after school my son and I manage to get a live match team game in where we are both on the same side
We are in the same room me on phone him on tablet
And it is a lot of fun
Because time is so short we don't get much time to discuss much and are desperately trying to plan or suggest a tactic or square to the other
Or to moan about the other players last moves etc
Being in the same room definitely gives us an advantage due
be

to the time advantage of fast verbal exchange
I assume it is not cheating because people talk about running two accounts on team games
Personally I think there should be a different category for that type of "team"
But for what we do ??
I don't mention it on the open game because I feel it might make it harder to get a game
Thoughts and comments welcomed

It's perfectly fine to communicate with your son verbally during a game. It's not considered cheating.
People can have multiple accounts on the same team and they might not do it to gain an advantage. In a real-time game, it's hard to commit with two or three account given the time limit. On the other hand, you don't have to communicate with your team over chat if you are the whole team. When I'm playing multiple accounts on a team, it's usually because it makes the game fill faster; another advantage.
If you and your son want to play a 2v2 against me, send me a mail :)

People voice chat as teammates all the time. And there's even been WZ meetups where players discussed games together.

So, no real issue.