But for younger niece and nephews i may be the only good example they have.
Yes, while that may (or may not) be true, I agree with everything MD said in her post above.
It's just like Fr. Wathen put it in the last minutes of that video I posted above, you need to watch yourself, which is
always very difficult to do successfully when one *puts themself* in a position of compromise. In your case, you're putting yourself in a position of compromise with your extended family because you hope to be a good example for your younger niece and nephews - who have other, full-time bad influences from your extended family, school, friends, TV, websites, etc. IOW, once they go home, they're fully submerged back in the mire.
It's a sticky situation, one that is better for you, *IMO*, by them knowing why you can have nothing to do with them - which is easy to say, but not usually easy to do.