We may have a local source, old overgrown windblocks and such. We may even have some family that would be getting rid of some 60 decent pines, which would have enough timber in them to meet our needs for this project.

And we may not end up hewing at all, it all depends on what works the best for us. This is for our own use, so I am my own client, and I'm pretty easy for me to work with
Hewing is the preference, but contraints of time and money might mean that we have a local guy with a woodmizer cut the logs to size for us, or even rent a sawmill and do it ourselves.
If we get sticks of the right size, we will hew. If we get sticks big enough to yield 2 timbers, we will at least saw the logs in half. We might go the route of hewing really big timbers out and sawing them in two. Again, this all depends on our supply. If we have to buy, we will buy dimensioned timbers and maybe treat the outside face with the axe for water shedding purposes.