Hey Katie!
Welcome back to the Disney Parks Mom Panel! Thank you for bringing us your question.
You are correct that the dates for
Mickey's Not So Scary Halloween Party (MNSSHP) have historically not been released until sometime in May. Last year it was May 8.
If you look at the dates from previous years they do seem to follow a pattern with some slight deviations year-to-year. Last year MNSSHP were held mostly on Thursdays and Fridays in October with some Sundays, Mondays and Tuesdays thrown in. Here are the October dates from 2013: October 3, 4, 6, 10, 11, 14, 17, 18, 20, 22, 24, 25, 27, 29 and 31.
My advice is to make your
California Grill advanced dining reservation then keep an eye on the
Disney Parks Blog for the release of the MNSSHP. If you do find that the dates are going to interfere you can changed your dinner reservation at that time.
I hope this helps your planning. If you have any other questions please come back and see me.
Wishing you a magical vacation and a pixie-dusted day!
Sue N., IN