Hey there, dove releases are fun. Here's my .02!
I"m sure the B and G will be standing somewhere specific with the crowd gathering around to watch the release. Usually, they also each have a dove in their hand, if not, that's ok too. Ask beforehand where this will be.
Make sure you talk to the bird guys to signal you when they're going to release them, I'm sure it's also in the program. Maybe you can PJ a couple shots of all the kids staring at the doves in their cages before the release too. Good stuff.
IF you're shooting by yourself, get somewhere you can capture the crowd and the B and G. Better to use a super wide angle lens if you have one. Frame the BG as the focal point and have the crowd as the fill but try to have tons of sky in the pic too. Keep your focus on the BG and try not to move when they release the birds. The birds will fly through your super wide frame and you'll catch the reactions of everyone as they fly away. Get ready to hold down that button and shoot away!

If you have another shooter, get them to do the spotting pictures or the face reactions of the BG or crowd.
This is one way to do it. I've done it like this before and it turns out great! Hope this helps and hope it made sense. Good luck!
I have a butterfly release in my wedding tomorrow!
Here are some pics. I had a 2nd shooter for this so I didn't go super wide, but I did step back a bit for the shot. After they released their doves, the rest of them were set free.