I had the same feeling about being "that mom" so I put DD into kindergarten at the age she was supposed to go even though I could have had her tested for early entrance. So then what ended up happening is that when she started K she was 2-3 years ahead of the other kids for math and reading and we did a full grade acceleration. It would have been far better to have her start early than do an extra year of preschool.
She did end up testing really high, above the 99th percentile, when we had IQ testing right around the time she turned 8.
But I still wonder about the effects of "enriched environment". We have tons of books, I talked to them about phonics and numbers when they were preschool age, I avoid letting the kids veg in front of the TV watching mindless things, I take them to museums, we play games, etc. so it's impossible to sort out even with somewhat older kids.
You can kind of see what is "real" ability if you give them something that they have no experience with, how quickly do they figure it out? When DS was one (not even 1 1/2) we had one of those tupperware shape sorters that looks like a ball with 10 shapes and DS would pick up the pieces one by one, analyze them for a couple seconds, then flip the ball around and around looking for the match. Meanwhile other kids his age had literally no interest in doing that, they would just throw the pieces around or put them in their mouths. It was obvious his ability wasn't just from "exposure", he was clearly fascinated by certain things. He was also obsessed with carseat or high chair buckles as an infant and would analyze the mechanisms, latching and unlatching, etc. If we went out in public and some stranger had a different car seat with a baby, he would make a beeline for it so he could figure out how their buckle worked.
It's important to be realistic about your child's abilities, but don't worry too much about being "that mom". If you end up being wrong, and your child does eventually "level out" it's not going to be the end of the world. Since I don't know ultimately how my kids are going to turn out, I advocate for what they need "right now" and keep try to keep quiet in terms of making statements like "She's going to be an engineer!" or "She's so smart!"
