You may have a valid case for age discrimination, and so might your co-workers who were fired. Are you in communication with your banquet manager and the previous GM? Would they be interested in joining you in a lawsuit against the company? You may want to discuss this possibility with them, and then schedule a consultation with an employment litigation attorney to evaluate the case. My firm, like many others, offers free initial consultations.
It appears that you are describing a pattern of older workers being terminated, but more details are needed in order to give you a thorough assessment of your case. I would urge you to contact an Arizona employment attorney for a consultation. My firm handles such cases. You can also contact the EEOC and file a charge of discrimination.