The Star Wars Marathon is slated for Jan 14 to 17 (Thu to Sun), so you'll be there during the marathon weekend. Marathon weekends are generally very busy, so expect high crowds in the parks. There might be some road closures for the race and I would avoid driving to the parks if at all possible (I went last year on the Avengers Marathon weekend and it took us 30 minutes to get into the M&F parking structure in the morning).
It's likely that there will be some attractions closed for refurbishment at that point. Haunted Mansion is often closed to have the holiday overlay removed. At this point, we know that the Rivers of America (Mark Twain/Columbia, Canoes, and Tom Sawyers Island) and the Railroad will also be closed (for a year or more), and F! will also be dark. The good news is you'll be there on a weekend (Sat/Sun), so they should be presenting PtN,
Disneyland Forever fireworks, and WoC on both nights.
Assuming the marathon doesn't change the schedule, there should be EMH/MM in DL on Saturday and EMH in DCA on Sunday. I would probably consider going to the non-EMH/MM park initially, but it might not matter a lot depending on what you want to do. EMH/MM means onsite guest (EMH) or guests with certain three day or longer tickets (MM) will have access to select attractions one-hour earlier than the general public. In DL, EMH/MM includes most of the attractions in Fantasyland and Tomorrowland. Over in DCA, EMH includes a wider selection of attractions, including RSR, TSMM, and Soarin'. They don't distribute FPs during EMH/MM, so you can always get one of those for the more popular attractions at opening. Basically, if you're goal was to ride RSR right at opening with minimal wait, don't go to DCA on their EMH morning. Same for Space or Star Tours in DL.
DLR doesn't release their operating calendars until about 45-days/6-weeks in advance and entertainment is often not added until much closer to the date. Dining reservations open 60-days in advance. You can often find prime dining reservations only a few days out, but I would still recommend making a reservation if you know you want to eat at a specific TS location at a specific time. I've noticed that they've been turning away walk-ups more often lately.
