Do you plan to sand it down first. If so, hammer down all the nails as this will ruin the sander. Rent a drum sander or a vibrating plate sander, all floor models.
I would use one of two products: My favorite is by the Flood Company called CWF-UV, it comes in many colors, and it has to be painted on. The second is: by Sherwin William's called Cuprinol, it can be sprayed on and back brushed.
Both will do a good job and will last about two years ONCE the surface has been saturated. Since your deck is 11 years old, it will absorb alot of product fast. So, you may need multiple coats after each drying.
Both are a stain/sealant and NOT a topical bandaid like the Thompson's Products.