Hi! We stayed at Riverside from Wednesday, Nov. 2 - Tuesday, Nov. 8 last year and we did not participate in any races. Jersey Week (short NJ school break) also started the second week and Tropical Storm Nicole kicked up closing the parks briefly after we left. Thus there were a lot of factors affecting our vacation.
I would think the Halloween holiday would be crowded too so my totally uneducated guess would be that the crowds would just continue possibly abate briefly with runners checking in later in the week. I wrote a trip report about our trip but here are some of the highlights I can remember about the crowds:
Both mornings (Th. & Fri.) in the parks were quite pleasant but the crowds got heavier throughout the days and evenings. We slept in Saturday and then hung out at the pool until it rained. We had to move two lounges together but there was actually room to swim in the main pool. We went to Disney Springs in the evening - crowded but manageable. Our resort wing had been quiet until Saturday night when the room above us wasn’t feeling well and kept us up from midnight - 4am. Sunday at MK started off quiet but got very busy and when we showed up for our dinner reservation at Be Our Guest we were told it would be another 30 minutes. We were tired and hungry so we had them cancel it.
Would I go at that time again? Probably, although from what I read Jersey Week and race weekend are usually in the same week. Last year Jersey Week came after the race weekend but perhaps some people came early. Not sure which resort you are staying at? but I would plan any activities - pool time, Disney Springs, etc. early in the day. Had I known what would happen to us at MK I would have made earlier dinner reservations too!
Good luck on whatever you decide! (Also are you eligible for any of the new room discounts?)