Straw (not hay). You should be able to get rice straw, or wheat or oat straw.

Wood chips: Call the power company and ask if they have wood chips from easement clearing. Or call a tree removal company. If they can dump a load on your place instead of making a run to the dump, they'll be happy.

It has to be wood chips. Controlling weeds over such large areas is a nightmare otherwise. Note that here it used to be free, but now most companies charge for delivery. I still get them for free (30 tons two years ago for the orchard) but it takes work.

These gardens are next to my house. I've been told that Pine/wood chips would attract termites. Is that true?

If not, I have mountains of Pine/horse manure that I can use.

Possible. I have no termites in Michigan, and alI mulches will attract critters, so I can not help you with that. But for mulching large areas, in a way that you don't have to worry about it for 2 or 3 years, wood chips can not be beat.

Termites like cardboard more than wood chips. Whether they like the chips depends on the species of tree. I don't worry about it.

Any material used as mulch can attract all kinds of insects because that material will create a nice habitat for them. However, many of us that have used various materials for mulches have found the concerns are vastly overblown.
I have not, in over 45 years of mulching, found termites where
I have laid down wood chips, cardboard, newspaper, or other cellulose products. I have found Centipedes, Millipedes, Pill Bugs, Sow Bugs, Spiders, etc. in those mulches as well as earthworms and if I had a good microscope I would have seen many species of bacteria and fungi at work there too.
What to use for mulch depends on what is readily available in your area, for free if possible. Deciduous tree leaves, straw, spoiled hay, wood chips, grass clippings are all possibilities.
Perhaps the link below can help dispel the myths surrounding wood chips as mulches.

Here is a link that might be useful: About wood chip mulches

kimmsr: great article in your link. Thanks. I have used arborist's wood chips for decades, with only positive results. I have to admit, when people warn me about termites or nitrogen leaching, I occasionally wonder if I'm doing the wrong thing after all. Since I just got a huge load from the tree service that took down some dead trees yesterday, and I have extensive gardens to mulch, I'm very happy for the reassurance in this thread and in that article.

Too bad the fellow and his machine aren't here to help with the spreading!

Kimmsr, I have to say that I have found termites in a pile of cardboard that was being stored for compost. They ignored the wood pile and went crazy for the cardboard.

nil, I said I have not found termites in cardboard used in the garden. You will find all kinds of critters in cardboard kept in dry conditions, anything ranging from termites to cockroaches have been reported in those conditions. You cannot compare grapefruits and mushrooms.

The cardboard was in the garden, and the termites were in the bottom layer in contact with the soil. So exactly the same conditions as if the cardboard were being used for sheet mulching.

I'm playing with paper and straw this year to develop a garden area for next year. I get several hundreds of those paper leaf bags and many small cardboard boxes. By layering these down and then covering with straw I hope to have a decent planting area next year when I retire.

Lloyd