The trees that are growing will produce more seeds. Those seeds will in turn help those trees become viable once again. It will take commitment from farmers to see to it that these trees have a place to thrive while they are multiplying. But they are lovely trees and they should be allowed to grow.
All most tress need is to be taken care of. If you water the seeds enough and give them a healthy dose of sunlight they will survive just fine in the end. We could most likely bring back every single extinct tree as long we had all the seeds from them.
They should plant all the seeds as quickly as possible. Every single one. Time is not on their side so action is required. If they want seeds for a museum they can get them off new trees. Seeds belong in botanical gardens anyway ...not in museums. Many ancient things reappear. Years ago, scientists found some rice in a pyramid.
I love the idea that old seeds could make extinct trees grow. If they are viable and could be sustainable that would be a wonderful thing. Between humans and massive extinction events, we've killed off a lot of plant and animal species. Renewing some would be almost miraculous and hopefully scientists can find ways to make them viable.