Ken,
I would avoid the pine needles as while wine caps are aggressive on hardwood, pine doesn’t play nice. Of the other two options, both are great. As a rule, straw will establish faster but the wood from the
pallets will last longer.
Not a bad mix is to cover the pallet wood with straw to avoid drying out. The straw will get inoculated right alongside the wood and will disappear surprisingly fast.
If really want to speed things along, lay down wood and cover with some straw. Inoculate and
water. Then cover everything with a layer of newspaper (2-4 layers thick) or cardboard, and add more straw (shredded leaves will work as well). The second layer of straw/leaves will simply hold the newspaper/cardboard in place. Water again. The newspaper/cardboard layer will help prevent evaporation from the primary wood layer and will stay more consistently moist but not wet—ideal. This can really get the wine caps fungus growing in just a couple of weeks, depending on moisture levels. In time the fungi will eat right through the newspaper/cardboard layer and go on to eating the top layer as well by which time you
should have some pretty well colonized wood substrate.
I hope this helps and if you have any questions, please don’t hesitate to ask.
Eric