It’s really difficult to say because each person and each situation is different, but I think it would be good - if you are planning to give your friends some material on the Mass - to try to avoid material along the lines of "IT’S A MORTAL SIN TO MISS MASS AND YOU’LL GO TO HELL :eek: !!!" and try to find materials which explain the benefits of Mass (and Confession).
With a very close friend, you could probably make a more direct approach, but with either approach, remember that it may not work no matter what you do.
I was once very good friends with someone whose faith I sometimes questioned (interiorly). We sang in the choir together and I believe she was involved in another volunteer group (don’t remember now). She liked to hang out in bars, and every once in a while, she would… ahem… “hook up” with someone. I asked her once, “How can you do that on Saturday night and then receive Communion the next morning?” Her response was: "So what? Everybody does it!? :banghead:
Some people just don’t “get it,” or take a much longer time than others to “get it.”
I would suggest that if you are close enough to your friends, maybe you can set up a date for a Sunday morning Mass followed by brunch together. (If possible, try to make it to Mass at a parish that is known for having a dynamic homilist who might wake your friends from their stupor!)