As PP said, you make all of your requests, including what you mentioned and the cabana on CC at midnight on day 125. In the days prior, you can email or talk to shoreside to obtain specific information, like the days and times for specific activities, hours of departure for port activities, available dining rotations and nights for special events (Pirate night, formal night, etc.) so you can request a specific rotation and adult dining accordingly.
Based on that info, draft your email in advance and click send at midnight. The emails are processed in the order received.