Welcome to the RoadTrip America Forum!
Three months opens up a lot of possibilities for a trip of this magnitude. Outside of the normal budgetary concerns, you should not have too much difficulty making this trip.
A recommendation I have is to pace yourselves, which you seem to have done by mixing in visits with family with being out and about on your own.
Keep in mind that one-way rentals for cars (like you have from Albuquerque to California) tend to have expensive fees associated with them.
I don't see Yellowstone listed in your post, but you shouldn't hesitate to make a stop there during your Montana-Wyoming leg.