Hi
Am in exactly the same position (much loved large garden, lots of plants (around 200 different types), got a bit neglected (before we moved in 2 years ago, previous owner got older), I have no time, two small kids..etc).
Spent the first year cutting nearly every shrub to ground (so I could see what was there), then last year redoing all the paths and crucially - laying more lawn. We can now see the wood for the trees and I can now start planting in the holes where I dug ugly/overgrown things up.
I have divided quite a lot last autumn (irises, penstemon, campanula) and took a few cuttings (penstemons were really easy), and am trying to reuse lots of plants that I already have.
I have a small veg plot so only did courgettes, tomatoes, peas - all really easy and grew well. If its cheaper to buy veg in the supermarket (carrots), then I consider too much trouble!
I also filled a hole with a rhubarb, which I'm hoping I haven't killed, but that should be pretty easy to look after.
We too had a greenhouse which we sold (sorry!) - it was looking a bit in need of help, with broken panes and so it went (DH fancies the space it was in for more parking (sorry again!), and its space is currently home to a huge pile of rubble (from the old concrete paths we had to dig up). I would have liked to have kept it, but really I didn't think I'd have the time for it for years, with the kids more grown up, to be honest.
I have finally found a reasonabley priced, knowledgable gardener to help with some of the more time-consuming or specialist jobs (digging up hideously suckered rose bed, pruning the pear tree), but it was tricky to find him amonst the large number of "gardeners" around here who just want to mow lawns and nothing more taxing.
But, as a result, I have developed a growing obsession with gardening - owning this garden has enriched my life. Even if some days and I love it and others it overwhelms me.
Sending loads of encouragement...I hope you can get to grips with it - I would love to hear how you get on.