Hi Pamela! Thank you for your question and for visiting the Disney Parks Moms Panel.
In short,
using Online Check-In will help simplify your arrival at a Walt Disney World Resort hotel so that you have the ability to skip the Front Desk and head directly to your room. In addition, you will be able to communicate with Disney Cast Members your room requests during this early check-in process… which will give them a little extra time to help accommodate your requests. However, I wouldn’t say that checking in a month or more ahead of your trip will provide an "upgrade" to your reservation, other than peace of mind knowing that you’ve already checked in and that you've relayed to Disney your requests.
Personally, I’ve found that Online Check-In is really worth the two minutes to set up. But if you would prefer to wait, that’s totally fine! However, as a small piece of advice, if you end up skipping the Front Desk, just
be sure to bring your MagicBand with you, or set up the Unlock Door feature on your phone.
If you have any other questions, please let us know. Tell Mickey I said hello and have a magical day!
Bryan