the 90+10 rule does work on the online reservation system. It still applies to only those staying at a Disney resort though.
The system just opened this past summer. You can play around on the system prior to your booking date. Just select a date that is currently in service. Disney only populates dates that currently within the window. If you click on the calendar icon, the dates included are in bold (or at least a little darker). Once you see what dates and times are available, don't select one.
A couple of things I have found:
1) There is a date range option. It lets you look for a period of four days. It's useful if you have a couple of must do restaurants. (Works a little better with the 90+10 option.)
2) You have to put in a requested time and the system will search for some period of time before and after. I'm pretty sure it is less than 90 minutes but do not know the actual window. So if you're okay with a 7:00 or a 9:00 PM dinner, you likely want to do a search on both. There is a modify search button on the results page that makes this easy.
3) The system will give you alternatives in the same general area if nothing shows in your particular search range. As noted in 2 above modify your times if you're flexible. Disney defines general area pretty broadly in some cases. The monorail resorts may show up with MK requests. Epcot may show up with DHS. the system will offer some alternatives. When you have places like Epcot with a lot of choices, all the alternative openings may not be shown. If you have another restaurant that you don't see on the list, you may want to do another search.
4) Originally the reports were that the system would roll over dates about an hour earlier than the phone system opens up. People have been reporting getting access at 2:00-3:00 AM Orlando time.
5) To get to the system, go to the Disney resort page. In the lower left hand corner there is a link for dining. The link allows you to look at restaurants by area by clicking the "Restaurants" link or searching for an individual restaurant. Below the picture of the restaurant is a "Book a Reservation" button that takes you to the online system.
The last part of your trip falls around MLK day. Crowds should be high at that time.
