I agree with 71Chally, its human nature to think the 'grass is greener' at a new opportunity, and I would follow the other excellent advice above and make as honest comparsion as possbible before I would give up a job where I feel I have at least some security right now. Saying that, you know what you need to support your family and if your current job isn't cutting it then you have to to what you have to do and hope for the best. I've turned down higher paying positions a couple of times in my career and each time I was way glad I did as things turned out. I've also worked for 8 companies over the last 32 years so I obviously made moves when they were the right thing to do at the time. Go to the interview and go with your gut, its worked for me.
Later, Jim