Can I register to be an organ donor without putting it on my license immediately?

I'm almost 19 and I've always said I was going to register to be a donor. I got a new driver's license when I turned 18 and it doesn't expire until I'm 21 which is 2 years away. Do you think it would be bad if I register to be an organ donor online, but wait until I get another license to put that I'm an organ donor? I don't want to have to go through the trouble of getting another license right now. Or should I wait until I'm 21 to register?