I say that anyone who makes it to 50 years nowadays DESERVES to have the occasion marked at least by being taken out to dinner with all the immediate family members. If you want to make it a Torah-dig occasion, maybe the sons and grandsons if any can make a siyum, and then it is a seudas mitzvah, also.
It is not so difficult to make this special occasion into a truly exceptional one, within Torah parameters. Each family member and friend who is invited should write down a special memory to be collated and bound into a “memory book” for them. If anyone is handy with a video, they can make a video presentation of family members being interviewed about their feeligns for the couple. Go for it.