You're welcome!
I think your best bet to see Mickey in a classic costume is at his house in Toontown. One thing to note about characters in DLR is that there are more "informal" meets than at WDW. So, as you wander the parks, keep your eyes open because you never know who you might meet (and when). In very broad terms, DLR has three types of meet and greets: the fixed locations (e.g., Princess Fantasy Faire and Pixie Hollow), the semi-fixed locations (e.g., Town Square or Buena Vista Street), and the random (e.g., walking through Fantasyland). The fixed locations are the "easiest" because they don't move and the characters tend to have a set schedule (e.g., they meet from 10:00 am to 6:00 pm). The semi-fixed locations means there are often characters there, but they may not always be there and you may not know who you'll see. The random characters are luck of the draw in terms of location and timing and character. The back of the Time Guide often has information about character locations and you can also inquire at Guest Services if you're looking for someone in particular.
In terms of the number of days in each park, it depends on whether you have park hoppers or not. If you do, then I would probably end up doing 1.25 days in DL and 0.75 days in DCA. Remember that on most days, DCA closes at 10:00 pm and DL closes at midnight, so if you have a hopper you can "hop" over to DL for the last two hours of the night. Although, if you do opt to see WoC, I would opt for the later show (10:15 pm), so that you can maximize your time in the park. I have heard that riding things like TSMM during WoC may help reduce your wait (not sure how well that works during the summer). You will need to get a FP and timing the FP to get the right show time (whether it is for WoC or F!) can be difficult. They distribute FPs for the first show first, followed by the second show.
Speaking of FPs...DLR still uses the "legacy" FP system (i.e, paper FP system). It's pretty similar to the version WDW used before they went to Magic Bands and FP+. It's worth noting that the FPs for character meet and greets (e.g., Olaf and Anna & Elsa), nighttime shows (e.g., F! and WoC), and the Frozen play at Fantasy Faire are not "connected" to the rest of the FP system. So, for example, you can get an FP for WoC and then immediately go get a FP for RSR. All attraction FP are linked to each other within the respective parks, but the two parks remain "disconnected" from each other. Meaning you can get an RSR FP and then immediately hop to DL and get a Space FP without having to wait for the time window to open or 2-hours to elapse (whichever comes first). It's something to keep in mind if you do plan to park hop. Also, note that DLR does enforce return times and there is no set grace period, so you should plan to return to the attraction within the time window printed on the FP. You can also try the
Single Rider Lines (SRL) if you don't mind riding separately. There aren't a lot of SRL, but it's an option to consider.
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