Yes you do more than enough! I don't think you should do any more unless you have the time and desire. If you need to cut back I think you should. Anyway, don't play their silly competitive game. Who knows why they do it, that's a whole other discussion that won't lead to an anser anyway. Also, don't worry about the times they don't need you, it sounds like you find things to do to help and it's great you are looking out for those times. Some of us don't have an eye for that and wait to be told what is needed.
I do have a few suggestions as far as communicating with people. You can also use something a voice teacher taught us. It was meant to spare someone hurt feelings after a performance that you personally didn't like for whatever reason.....You would say something like, "What an interesting interpretation of the song".
In our lives you could say, "That is an interesting opinion", or just, "hmmm, interesting I'll have to think about it" Then actually forget about it but you've acknowledged the other person even if what they are saying doesn't help you. Or "No worries" (I use that one a lot).
Another one is telling them what you can do. So in the example above. "To help with the festival I can watch mom1s kids and mom2s kids so you have two people to work the entire festival". If anyone questions your "visibility" as far as volunteering just tell them you are comfortable in supporting roles and are very happy. Thank them for being on the "front lines" and let them know you are willing to help (I know you've done this)
About the pictures, I think they should have explained if they couldn't use them as to why. I know at our school, space is a premium so they try to get photos that have a group of kids instead of one or two. They also have a set template from the publisher and only have complete control over two pages (Halloween). So unfortunately Creativity is squelched for efficiency, cost effectiveness and timeliness.
It really sounds like there are a few things going on here, there are some inconsiderate people and lack of communication. I think what helps if you are VERY specific about what you offer (it sounds like you already are though). Also, just because other people aren't appreciative doesn't mean we shouldn't be. If you see someone working hard, Thank them or acknowledge they are doing a lot of work. It is hard, but root for those who may not be your friends or may not have supported you.
I learned that over the past year or so people can have more going on than we know, or just unrealistic expectations of themselves. They get themselves all up in a dither. Try to be the calming voice. To do that you can't get caught up in the game, just do what you're doing, you are doing great, don't let all the political/emotional stuff affect you, let it drop at an imaginary force field around you. All the Best!