Hi Michelle,
I'm not doing this trip but I do have both walking boots and trail shoes as I do go coastal and country walking.
zippy's suggestion of trail shoes being better than trainers is definitely a good one.
Please bear in mind though that walking boots and trail shoes tend to be a snugger fit than normal shoes so you may need a larger size.
I wear one size bigger in walking boots and trail shoes than any of my other footwear.
Also, I think that if you will be doing a fair bit of walking, it is worth investing in a some proper walking socks. These will offer more cushioning than normal socks and are less likely to give you blisters. They can be rinsed out and dried overnight so you would not need to buy many pairs.
And when trying trail shoes on it's best to try them on with the type of sock you'll be wearing.
I know it's an additional expense but it's got to be better then risking ruining an expensive holiday by having aching legs, and sore and blistered feet?
Hope that helps? Enjoy your trip.
Julian 🙂