If there is one good piece of news I can deliver you its that people whose father own big companies tend to do VERY well in their applications. This is only normal (especially if the company is big), as you are essentially a guaranteed success story for them (so, if your goal is: I will take over my dad's company to become CEO of a 5000 large workforce, you are getting IN).
Your 660 on your GMAT is however, a bit unfortunate, and might put some top schools out of range for you (depends a bit more on the company, your work experience etc.). I don't know if its worth a retake, but it might be worth considering it. For example with a very strong GMAT plus a very big company, all of a sudden HBS becomes possible. So it might be worth it for you.
Are you unique enough? Maybe that is the wrong question. The question should rather be: How do I MAKE myself unique? What can I DO to stand out? to PROVE my success?
As for your final question: Yes I think we help a lot! Otherwise I wouldn't have founded a company which provides such assistance to folks such as yourself!
We have seen LOADS of applications from loads of folks, and we can help you get out your unique story in the most effective way for the B-school to give you the best possible chances to reach your dreams.