What age

So my husband’s mom passed away when he was 13 years old.. we have a daughter that’s 16 months old. We would like to take her out to his mom’s grave and plant flowers every year. I’m just not sure what age to start at.. his mom always wanted a little girl, but that didn’t happen and she was taken at a young age from a Brain aneurysm. Anyways when I got pregnant, it was a very difficult, no way she shouldn’t be her kind of pregnancy(someone was definitely looking out for her). I bleed for 20weeks, heavy bleeding, to the point the doctors said they highly doubt she had a heart beat, well she did and keep fighting, starting dilating at 23weeks, couldn’t keep food or water down by 22weeks until she was born at 34weeks. She was actually a pretty decent size for a preemie(5lbs 11oz). I will always think his mom was watching over her and still is. Anyways sorry for the long story.. when would you take your child to a gravesite to plant flowers 💐?