I have the same problem. It is a shame that we are not able to share tags and tag hierarchies. It doesn't work even for viewing and searching of existing tags. And nothing changes for years with this problem.
I believe, there is no conceptual problem with this. It can be designed and implemented with no problem. It is just not a priority for the Evernote team.
I think, in current situation creating a joint family account for family tasks is the best option. But this means paying for an additional license.