Does your father like to garden or is this a new hobby? Did he have a vegetable garden at other homes?

Some people like a larger garden with rows of vegetables...and enjoy getting out the roto-tiller and chopping up weeds in the paths, every week. That's fun for them! LOL Other people like beds with gravel or brick paths...or maybe raised beds around the edge of the yard. It all depends on what you're growing and what you like.

If your dad has never gardened before, I would probably try a small garden patch (dug up dirt area towards the back of the yard) for larger vegetables...and a few raised beds, closer to the house, for smaller veggies and herbs. This will give him a chance to try it and see which he prefers.

He might like both, but if he likes only the raised beds, the patch can go back to grass. If he likes the patch...maybe some flowers and herbs can go in the raised beds. Just an idea :)

WOW! That is something else!
We need to know a LOT of things! (Many of which LL asked!)
we need to know your area, type of soil, if it needs work, which way it faces, how much sun it gets, do they have pests, are they semi creaky (do they need raised or raised UP beds), Can they get down and dig/weed/plant? Can they (or do they want to)compost?
A greenhouse is fun, but NOT required. If they're first timers probably NOT!' I'm a gardener that started in my 40s and have made my garden bigger and bigger BUT my back has really become worse and worse!
You don't want to make MORE work for your parents! But a nice garden that is manegable would be nice!
I used my GH as a place for my flowers to not freeze and a place to sit during the winter reading!
It's a lovely thought