Rather than OUR thoughts what would you like to use the garage for? Would you use the gym? Lounge area? it’s personal, what I would prefer is irrelevant.

maybe somethink like this?

You have wonderful space. Using the vacant garage for shelter or 3-season space is a great option.

Our former property wasn’t as large or provide opportunities like yours but we did install serpentine
gardens, firepit and steppingstone path. A video showing the final result follows.

https://youtu.be/H5t9G-Gujqw?is=BC5vyfLFqlG2OJUs

Because of the multiple deck entrances, multiple accessory structures, and change in elevation, a professional architect and landscape archtect should be involved for a successful outcome.

Not all info is apparent from the photos and drawing, so this is just conceptual. Two things I notice immediately that could be considered in a design:

• The pavilion seems too visually disconnected, just a "bridge" to access it, and the very haphazard deck footprint exacerbates that. So in order to integrate it more seamlessly with the main house, extending the deck out while simplifying the footprint would help.
• The garage roof varies, so that should be respected with the layout of any changes to the garage. The secondary roof section of the garage seems to offer an opportunity for a fireplace and patio seating area in front of it.