If you already have a lot of your application done, go for it. When I shadowed, I talked to optometrists, and it was the same week or the following week they wanted me to come in. Even if you could do a few half days with one at a clinic, private practice, commericial, etc. I'd think it would be better than nothing! Not all the schools have a required amount of time you need for shadowing.
It is not cheap to apply, but does it outweigh another year of waiting? You won't know if you are rejected until you submit your application. Just go for it, and if you don't get in, you already have some shadowing hours for next year's application.