Design process : which is the best moment to include developers in the process of software development?

I'm a UX designer in a small software development start up.

Until now, I've always worked with developers since the beginning of interface creation, because I don't want to lose time working on many features and interfaces to discover we can't develop it at the end because it would be technically impossible.

I also believe that if I share with developers the design problems I meet since the 1st step of the process, and if they see me working on, they will feel more involved with the project, and it will be easier to work with each other until the end.

Until now this way to work worked! Perfectly. It was easy and efficient BECAUSE I was on a team with developers who really don't care about design. They trusted on my recommendations as I trusted on their code. Each of us did his work and shared with the other, like a ping-pong communication game.

Today, I had to work on another app development project, with another team, and It was very complicated. Here developers care about design but they are not designers and they don't know how doing good design. So they wanted me to change the interfaces, not for the users but for THEM. They would choose the interfaces that look like what THEY like. But they are not the final users.

So now I have some big doubts about how to work with them or to share my mockups with the team. I really don't want them to feel frustrated, because it's a good thing to have developers who care about design, but I can't let them do whatever they like just because they want to, or just because it's easier to code, or because they like a UI framework and they don't want to change anything on their way to work.

For me, because I'm a UX designer, the final user has the priority. I don't say my point of view is better than theirs. What I want is only one same way to make our application. Only one TEAM point of view. Together.

Do you have any advice about how to communicate, or any good design process to help me?