Hi John,
As of today, the park hours are not available for May 2012 yet; however, I did check the last week of April 2012 which has Wishes at 10:00 pm. So my first thought would be that that time would carry over into the first week of May. If that is the case, I'd opt for a reservation between 8:00 pm and 8:30 pm which provides you plenty of "cushion" time to be able to enjoy your birthday celebration dinner. But I do want to share with you that as a guest at California Grill, you can dine earlier in the evening then return for the fireworks that same day (they'll ask to see your receipt).
So, I'd mark your calendar to make your dining reservations on October 31, 2011, if you are a Disney resort guest (you'll be able to make 10 days worth of reservations when you are 180 days away from your arrival date -- you'll need your confirmation number to do this). They can be made by calling 407-WDW-DINE or online by clicking
here. If you aren't a Disney resort guest, you'll be able to make the reservation on November 5, 2011. Make sure and include a notation about your wife's birthday. On October 30, 2011, I'd also click
here to see if the May 2012 is available yet. If it is, you'd simply need to click on the specific date to see the time when Wishes is scheduled (subject to change, however).
Wishing you a wonderful trip as well as a fantastic dinner; I LOVE the California Grill! Please let us know if we can help again. ---
Kara