You are a man (or woman) of few words aren't you?
If you are worried about them showing in your playtrough, then don't. If they show up, they will be cameos. And bioware's cameos are well executed. Did wrex even show up in your playtrough of ME 2 and 3? It will be the same thing, we will get wrex, you will get Wreav or some other random krogan. As for Liara, she becomes the shadow broker with or without Shepard's interference, so she will be the powerful shadow broker matriarch, like it or not.
No, you are fundamentally wrong. As in you didn't grasp the underlying principle of ME:A. It plays far in the future, in another galaxy. It is as disconnected from the trilogy as possible. If you get some codex entries about The Shepard and their crew, then that's quite a lot already. Cameos? No chance in hell.
I already explained it earlier: Anyone has the potential to die, so no one can show up in a game that won't impose a canon on the trilogy. To make everything possible we can't involve a lot of the things that happened.
Please get your facts right. Everybody can die. Refusal ending, the entire galaxy gets harvested, the Reapers win... and then the next cycle defeats the Reapers with the help of Liara's data caches. High or low EMS doesn't matter.
Even if we ignore that big fact, the only companions still alive in the future would be Liara, Grunt and EDI. Everyone else lacks the long lifespan or is too old already. EDI has a 50% chance to be dead (Refusal and Destroy), so that's another strike. If the future is more than a thousand years then no one is alive, no matter which ending.
If everyone died, then they have no kids either.
Now we saw a N7 character in the trailer and know our PC will be human. To me that means the only logical way of this happening with all possible endings is if they left for Andromeda before the finale in ME3. No matter what happened in the Milky Way, they don't know and maybe can't go back. They are on their own in a new galaxy. And since it happened before the finale, no one we know can be in Andromeda now. Certaintly not their kids.
Otherwise BioWare would have to **** up their game right from the start just to pander to the fans and squeeze in cameos. I know they never cared all that much about logic, plot holes and consistency in the past so there is a tiny, tiny chance you'll get your wish. At the cost of a potentially great game that will ****** away that potential for cheap feelings. I definitely hope BioWare learned from past mistakes and won't do that.