Children's ideas

My wife and I are excited to go back to Yellowstone this year in June. We will be taking placement of foster children this April and we have no kids of our own. I remember the Jr. Ranger program was always a highlight of my trips when I was a child. Does anyone have any other child friendly ideas? We will be there from June 4th to the 11th and staying at old faithful inn. We do not know the age range of the children yet but it will be between 5-17. O also any items we should bring that would be helpful for traveling?