RIR enjoy the name recognition in the chicken world and most beginners want them as their first chickens. Personally, I don't feel that's the best place to start. There are 100's of beautiful and different breeds out there. Add all the feather patterns and colors available and you literally have 1000 different combinations to choose from. Some hatchery RIRs also have the reputation of being aggressive bullies. The first thing to do is select breeds that are suited for your climate. Cold hardy, heat tolerant. Are they primarily egg producers or do you want birds that will be decent meat birds in the end? With children, it's important to have quiet hens. They will be picked up and carrier around the yard, Kids are also going to name them so it helps that they look different enough so they can tell them apart. 25 red hens all look the same. This will also help you distinguish the layers from the liars as different breeds will have different looking eggs and colors. Maybe let each child select a breed and get 3-5 birds. That way the children can easily distinguish "their" hens and take ownership of them. A variety of hens will produce a colorful egg basket making chicken chores more fun for the kids too.
25 hens to start with is a lot. They will eat on average 50# of feed a week when mature and can produce upwards of 12 dozen eggs a week. You can always sell the extra eggs and offset some of your expenses but there will also be time when you are eating eggs for BL and D just to try to keep your head above water.
I can say from 50 years experience that Percheron chick has given you some great advice. I can attest to the aggressiveness of hatchery RIRs (particularly the roosters), and would suggest starting with breeds that have a well deserved reputation for being friendly, calm, and gentle such as Australorps, Orpingtons, Brahmas, Sussex, Cochins, or Faverolles. These are all great breeds for children (potential lap pets). If egg production is a priority the best layer on the list (and the best layer among the standard brown egg layers) are Australorps. A Black Australorp holds the brown egg laying record with 364 eggs in 365 days. Cochins are the poorest layers on this list, but they are the best brooders and mothers. The other breeds on this list (Orpingtons, Brahmas, Sussex, and Faverolles) are all good layers.