Welcome here this site! What a dilemma to leave the WT world, many are stuck in your position. Spend your time with your grandchildren as much as possible. They are your ministry! Speak in 'unconditional love' ways to them. Very important, to not contradict the WT and your daughter. But express your love them 'no matter what always' (they will not hear such talk in KH). Help them to be interested in all the positive things in life, the now & today everythings. Maybe try to do special things with them on their school vacations, during holidays and birthdays times, (maybe not on the immediate days) but special 'fun' things around those times. So they have good memories of special times with grandma. They will know the difference between those times, as JW special days are no memories at all but are only a blur for them.
Celebrating the 'seasons,' not specific holidays. Getting together and making cookies, is a gingerbread house with graham crackers and candies pagan? Make a snowman, etc. Can a subtle way to make seasonal (winter, spring, summer, fall) keepsakes, pictures or things collectible for them (you keep till they are grown). Make grandma's house a 'wonderland' for them. Build a fun 'philosophy' wall. Plaques, some serious, some lighter. "Love, Joy, Peace" Serenity Prayer. "Whatever!"
You can be hopeful, but it will call for such patience. It will call for you to have and show more joy of 'this' life as you turn your back from the depressing life of JW life.
So many best wishes to you!