Here is what I believe a tick, there are a lot of them, between the plywood and 2x4 of the coop, what is the best method to get rid of these, I haven't inspected my 3 chickens but im sure they are on them, how to I treat this

Guineas.

my chickens will eat them, but the problem lies within the cracks of the coop, where they meet together the chickens can get to them

Food-grade diatomaceous earth from the feed store.  It's completely safe to use on chickens.  Sprinkle it between the cracks and elsewhere inside the coop.  The tiny crystals of silica have a cutting effect on the joints of insects which is how it kills them.

ETA:  You can use them on the chickens themselves and I'd set up an area they can use as a dust bath if they already aren't doing so.  Dust baths help keep parasites off their feathers and skin.

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This.  

Your other option is to use expanding foam to seal up the cracks.

+1.  They're even tastier than the chickens.