is making an organization with website good?

Yeah, that's cool! I agree with the other answer---focus on the impact and why it was important to you. But yeah, a website is great! Might as well include it.

Technically, the website is a good way of publicly displaying the work your organization has done and reaching out to potential students. It doesn't matter what your domain is; admissions officers aren't required to check out your website (and mostly don't have time to do so). I think providing art tutoring is a good way to give back to the community, but you should emphasize more on what the organization does rather than the fact you have a website.

That is a good way of displaying your work for things like scholarships, but there are so many "organizations" by high-schoolers now that in order for it to make a difference on your applications, you need to really go above and beyond and achieve great success in helping your community (such as receiving national or global recognition for your work).