What should I do with the money I took from my grandmother without her knowledge to buy jewelry, and she passed away before I could return it, knowing that she was keeping it for funeral expenses, and my uncle and father covered those expenses? And is it permissible for me to donate it as charity?

Taking the grandmother's money without her knowledge and permission is an aggression against forbidden property. One must repent to Allah Almighty and return the amount to the heirs. It is not permissible to give it as charity because its owner exists. The expected negative assumption does not exempt one from returning the money to its owners. It is sufficient to return it to them without their knowledge of the details.