DONT GO 4 WOOD!! The menage at our yard is woodchip and it has turned to compost and it is really deep!! i would go for sand and rubber or sillica sand
Yard I have moved to have a woodchip surface (easiride) and I love it, rides much better than any of the sand/rubber surfaces I have ridden on and both my horses go much better on it. It is not deep at all and seems to have some "spring" to it.
Would go for sand and rubber if you want longevity of the surface - woodchip does break down - old yard I was on managed 5 years before ripping it all out and replacing with sand/rubber (riding school but that arena not used so much)
We went silica sand and startrack rubber and it's brilliant