That is good news to hear that you will be going down to the DLR in October and to see the new nighttime shows. It will be very interesting to see how the 60th Diamond Celebration affect the Halloween season this year including the Christmas season as well. We already know that Believe...In Holiday Magic fireworks won't be playing this year with
Disneyland Forever fireworks. The spot to watch the parade is from MS where the buildings on MS will be video projected for Disneyland Forever fireworks. I just wrote on my latest trip report about how long and what spot it was where I watched the parade and fireworks. I would say at least 2 hours for a spot on MS by the buildings might be the max in order to get a curb spot when you go in October. There might be some groups that will wait that long to get it but I can not see it like during the first few weeks during the Diamond Celebration.
After the last float from the parade went by, I went straight towards the middle of MS to get the middle spot to see the fireworks. The CM's told the guests before the parade that they are clearing the sidewalks for the fireworks. So when the last float goes by, you will have to move on over to the street and get a center spot to see the fireworks. I would say that it wasn't that great since my tripod and I am not that tall but it was decent where i was watching the fireworks after the parade passed by.
Here is my spot on the 26th of May for the 9:30pm Disneyland Forever fireworks
The projections on the buildings on MS.
Another spot to consider is seeing the Matterhorn which will also be projected for the fireworks which you might want to get a spot between the buildings on MS as well as see the Matterhorn when you go on the streets.