250’ separation should be plenty!
If you want to do logs and straw next to each other, that should be fine. But keep in mind the life cycle of the fungi. Fungi (oysters for our sake) infect wood, digest it, undergo sexual reproduction inside the substrate (wood or straw) and are happy to continue to do so until they exhaust their food supply at which point they sacrifice a part of their “body” to push up a mushroom and release spores (asexual reproduction) into the wind, hopefully to land on more wood and start the cycle over again.
My point is that as long as the mycelium have food (such as the partially intact log), they won’t produce a mushroom. If you are growing oysters in straw surrounded by logs, the actual fruiting (mushroom) might not occur until the logs are decomposed, well after the fungi has devoured the straw (it just found a new source of food and moved the party).
In am not saying this is going to happen. I am saying it is worth considering. My suggestion is to have straw beds and logs close but not touching each other (I think 1’ separation would be fine, but you can widen this if you like). Actually I like the idea of having a fast-growing, quick-producing bed and a slower, longer producing bed.
When the mushrooms have finished fruiting, they leave behind a wonderful compost that can be used in a garden bed. I actually make my garden beds so that they have Wine Cap mushrooms devouring wood chips right in place under tomatoes, yielding up great tomatoes and very fertile garden bedding (I don’t know if this is soil yet, but I do grow in it.). If you are interested in making mushroom compost garden beds, I can help you with that too.