Anyone brought their LO to cemetery before? To pray for the deceased? Is it okay?

Depends on your culture and personal preferences. In mine, I know some parents would prefer young babies to not go as they are "weaker" and supposedly more prone to disturbances (if you do believe in that). Logically, cemeteries are usually hot and have very little shade and can be quite inconvenient if you need to change or feed baby (unless you have a car). Personally, I started going to cemeteries with my family when I was around 10-11 years old. I guess I was old enough to understand and also not throw a tantrum if it gets too hot or uncomfortable.