Yes I remember your garden. I would keep things simple so a nice lawn for the kids to play on, surrounded by a few trees and shrubs. If you go for evergreen shrubs they tend to be low maintenance. Things like Ceanothus, Photinia Red Robin, Hibiscus and Cistus. You will need to check whether the different areas are mostly sunny or shady as this is vital. I’ve also noticed there are a few awkward level changes so I would remove them, level the soil and add more lawn. That pond area could be emptied and it could become a herb bed, as it’s near the house. It needs to drain well so if you could add drainage holes if it doesn’t have any. Herbs need sunshine and need quite a sparse soil, garden soil from another part of the garden will be fine. You can can add grit to help in drain. Of course herbs grown on any sunny site. A nice patio is always welcome. My favourite paving is Indian Sandstone and it comes in many shades.

Advertise your greenhouse locally, particularly if there are any allotments nearby. Allotment holders are generally keen recyclers and reusers. Am sure someone will want it and be willing to take it away.