I am not sure what the best option is but we are also going either on the
15th or 17th. We are doing a split stay so that is our "moving" day and I have my hopes for a late TS breakfast around 10:30. I am thinking of having an easy day, check out the new resort and head to the party early.
My other thought is just go to MK anyway on that day, watch the fireworks and water pageant from the GF and do RD at MK the next day. If I do that, we will do the party on the 17th which would be our last night there. Decisions decisions! I think the 15th is a discounted night for the party. We did a discounted night last year and it did sell out but it was great anyway. I want to wait to closer to the date to get tickets but I also am afraid those nights will sell out and then what do I do?
I am not sure if there is anything out there to tell us if any particular day of the week is better then another. Also, I would like to find out how many dates did sell out last year and how close to party time it did. Good luck with your decision.