Can tickets to Gulangyu be bought in person a few days before at the terminal?

Can I buy tickets about 5 days for the ferry ride to Gulangyu about 4 or 5 days before i.e. I arrive in Xiamen on a Tuesday and would like to buy tickets for Saturday as in between I will be going to Wuyishan and returning to Xiamen. Which is the correct ferry terminal for foreigners? The information I've found online is conflicting, and I can't seem to buy tickets online.