as far as i know, employers can not discriminate against an applicant's age, race, or gender. Your main worry should be getting the visa in the first place. Magiging issue mo at your age is the points that you can claim upon submission of EOI or expression of interest. Dahil over 40 ka na mas maliit points mo. You can still make up for it, ask your wife to take IELTS, claim points kung makapasa sya. If she has valid credentials and work experience, and her industry is in the SOL list, you can also have it assessed and possible din magclaim ng points.