I have done it 3 ways, TS at the Plaza eating with ressies at 4 something and then heading right over to Tomorrowland, did the picture, then started rides.
Also, 4 something CS at Cosmic Rays, then rides and picture right before leaving
and lastly, dinner at Grand Floridian Cafe at 5:00 (earliest I could get) and then heading over to party, rides and picture late.
What I will do next time is dinner at the Plaza with ADR's for 4 something, head to Tomorrowland start enjoying shows and rides and do pictures right before leaving.
Reason, Plaza was a nice relaxing meal to start out the evening, CS is OK, but not as relaxing, and eating at a MK resort, just got us there too late. It was our most awful time, and we only did about 3 rides because everything was just up and going and crowded already by the time we got there.
I would go to Tomorrowland then right after eating at the Plaza and start doing the rides and shows there, by 5 or so the non party people really start heading out of the park and the lines are almost walk-ons, by the time they open up the rest of the park at 7:00, you've had allot of fun doing the stuff in Tomorrowland and are ready to enjoy the other things in the park.
At our first party everyone said to get your picture done right away, first thing. We did that that first year, right after eating at the Plaza and still waited in line about 30 minutes. This was at about 5. Then we were walking around towards the end of the party in Adventureland, and the CM's that were doing pictures were standing outside, asking people if they had done their pictures yet. There was no line!!! So the other two times we waited til the end to do our pictures, both times, no lines.