I think it is a WONDERFUL idea! Afterall, they see you as a Grandaddy or Uncle. It is not right that they have to miss out and nether do you. Call and talk to the parents, I'm sure they would jump up and down to see you stay in their lives!
BTW, I think you will be back in C's life. Give her time, like my H they are dealing with their own guilt. Patience is the key to DRing! So grab it and wait! It may be just around the corner. As we both have seen here on the DB, just when you think it's over, that's when the R begins!