Well congratulations to you both on your anniversary today!
Model railway layouts can take up an awful lot of room and not just the layout itself - there's all the boxes and boxes of stock to go with it. Integrating your layout into the garden is a good compromise. Even with the two viaducts on my layout visitors rarely notice it's actually a model railway running round the garden. It adheres to the perimeter more or less and you don't need to step over it to access the garden itself. I believe a large majority of modellers look upon a garden railway as a last resort after discovering there's insufficient room indoors but in my view it's a location worthy of serious consideration whatever the case.