I think it's a good idea.
As a supplement, I'll give a brief overview of how this is viewed overall in Germany.
Children who died before, during or shortly after birth are generally called Sternenkinder (star children), but the terms Schmetterlingskind (butterfly child) and Engelskind (angel child) also occur. Since many things are regulated in Germany, there are even legal regulations for this.
The term refers to those who, due to additional requirements of personal status legislation (in Germany, at least 500 grams of body weight or, if less than 500 grams, at least reached the 24th week of pregnancy), did not get an entry as a person in the birth register. The term was used over time for more and more children who died prematurely. At the beginning of 2013, the law on civil status was amended so that parents of stillborn children - even retroactively and irrespective of their birth weight and the duration of pregnancy - can have them registered in the civil register.
For some time now, the pink and light blue ribbon has been used as a symbol for these children.
It symbolizes the memory of babies who died before, in or shortly after birth. These include: "miscarriages", "stillbirths", SIDS = sudden infant death syndrome.
This symbol would not include older children. However, I would have no problem with using it for all deceased children, although I would intentionally not specify the age, everyone must decide for themselves.
As my father once said, "You can be retired yourself, but to your mother you will always be a child."