I am making a 'quilt' for my bbysitter. I want to make a chenille one. When I go to sew through the 6 layers should I use a stronger needle? Like one for denim maybe??

Yes, I would. It will save a lot of frustration if you use a 14/90 or even a 16/100. If those break on you go to an 18 but either of the first two should work.