Jim Macklin had some good ideas.
I would agree that you might want to consider having someone else be the
CFI to avoid conflict. You can supplement Mooney time for practical
experience on family trips.
Definitely consider the taildragger for primary training. It is much
more fun, they will learn more, and you can have fun with it, also.
Train for the PPL in the taildragger. The skills acquired in the
taildragger will benefit them in future flight training. The
high-performance can be added later in the Mooney.
Buy or lease will depend on you finances.