Hell yes, I agree. My parents treated us as adults, probably from too young an age really. There'd be no secrets and they'd discuss everything in front of us, about finances, work problems, changing jobs, holiday plans, etc. One of the benefits of us all sitting down for an evening meal at the dinner table every day without fail (it was non negotiable), and over dinner, it was the time to talk. When we were young, we basically just listened to the "grown up" talk, but as we got older, we'd participate.
Luckily, OH and I have always done the same, right from when we started dating, always discussed everything, agreed everything, not once did we have any nasty surprises or disagreements, as we'd discussed/planned all important things in advance. OK, you lose the spark and spontaneous, but I'd rather that and have a calm life, than lots of arguments/bickering etc when one of us does something the other disagrees with or doesn't know about. Life's too short for that kind of drama.
We've done the same with our son. We soon stopped the infantile "baby talk" of silly names/words, etc before he even started walking, and called things by their proper names, and generally spoke "grown up" from the age of around 1, I suppose. Likewise, we adopted the "family meal" approach and would openly/happily talk "adult" between us, whilst he was sat at his high chair at the same table, joining in the conversation as he grew older.
It meant no surprises, misunderstandings, etc. He was part of the "decision making" process, even if he wasn't young enough to make a valid contribution, he heard our decision making processes and knew what was going to happen in given situations, as we'd pre-planned. As he got older, his participation increased, and by the time he started secondary school, he was just "another adult" around the table really, starting discussions, etc.