I'd accept you! haha
Which schools are you applying for? You have PLENTY of shadowing. I know some schools do require 100, so either way you're well on your way. Volunteering at an arts therapy center is going to look REALLY good to them. Any volunteer work is great, but this is even in the right area. From what I've gathered, most (if not all) OT departments are looking for the person who gives to the community and will contribute to the department. Grades are important, but OTs have to be people-oriented.
It looks like you have it all - you have a fantastic GPA, proof that you are interested in people and want to help your community, and you already have plenty of experience hours shadowing an OT. My school suggested shadowing at various places, so I ended up splitting my hours between 5 facilities: outpatient clinic, pediatric outpatient clinic, ICU (I think everyone should shadow ICU... that was intense), nursing home, and the pulmonary floor of my hospital.
Even though everything else looks great, still think of ANY achievements you can list, no matter how small -- even back to high school. Any awards (sports, character, academic) - any scholarships - any time you made Dean's list - everything.
Good luck! Sounds like you'll have no problem getting into the school of your choice!