it is not up to you to guide them rather it is allah who guides whomever he wishes. whatever wealth you spend it is for your own benefit as you do not spend but to seek allahs pleasure and whatever wealth you spend will be repaid to you in full and you will not be wronged.
ليس عليك هداهم ولكن الله يهدي من يشاء وما تنفقوا من خير فلأنفسكم وما تنفقون إلا ابتغاء وجه الله وما تنفقوا من خير يوف إليكم وأنتم لا تظلمون