Space is expected to come back Nov 3 so at the very least it could help draw out some crowds the second day and of course, if you wanted to catch a ride on it I'll keep my fingers crossed and send some pixie dust for good measure that it keeps to the schedule and you get a chance to enjoy it for your nephew's big day!
Going midweek on a Wed-Thur the crowds are likely to be much lighter, especially compared to weekends. Also, you'll be there right in between seasons with Halloween just ending and Christmas not yet up so there's no specific event in the parks to draw lots of people. There is Dapper Days going on that weekend, I believe, but being in the parks Wed/Thur you're only likely to run into just a few of the first arrivals, with more of them coming closer to the weekend.
That being said it is very possible that the lines for everything else will be longer, but usually Disney is pretty good at scheduling overlapping closures at low crowd times so as not to create a huge negative impact on guest experience. Also, I would just say to make good use of FPs for what is open, and ride the headliners that don't have FPs right at park open (i.e. Matterhorn) or get in line right before park close (Peter Pan is a great choice for this)!