First, if there's a chance that you may end up in litigation over this, please change the facts to fictitious parallel ones (relevant state, e.g.) to lower the chance of this being found by opponents. What goes on the internet stays there and can come back to haunt people in litigation, where anything you say that can be twisted against you may be brought in as an admission against interest.
Now to the matter.
Trademarks are marks used in trade to identify goods or services as coming from a common source. They can continue forever, but only so long as they continue to function as trademarks for the business. Marks don't exist as marks without being connected to a business and, generally, failure to use a mark for three years gives rise to a presumption that it's been abandoned, although that can be rebutted by showing evidence of an intent to continue using the mark. That argument would be hard to make after over half a century even if the business were still around.
Nevertheless, there are special circumstances when famous marks and/or famous people's names are involved. And this is not the first time someone new has tried to resurrect a well-known older now-defunct mark. Here's a
1999 article which discusses some of the issues that arise when a newcomer tries to take a free ride on an old, but still recognized mark.
I'm not up on the current state of the law in such circumstances, but perhaps one of the active TM practitioners here will be able to address this. Keep checking after the weekend.
As for copyrighting the old recipes, even if possible, that would not give the sort of protection you're looking for. Copyright protects the form of expression, not the content of what's expressed. If the information in the recipes has been kept as a family secret, there might be some hope of protection/market for them if they can be treated as a trade secret.
Good luck and keep checking back for other posts.