The Church History ABC's is a wonderful resource to accompany an ABC's curriculum (and there are several free ones out there!). It's really a great resource to accompany any home library. It has just the right amount of information to wet a child's appetite for history. Being geared for kids [roughly] 4-8 years of age, it has the potential to offer plenty of fun information for a 4 year old, while allowing for further study for an 8 year old. In addition to having some extra facts in the back of the book, it's a great opportunity for making a library visit to check out each person individually.
I appreciate the extra words they include for each letter to help a child understand each letter has a sound and the hero (or heroine) mentioned was not just coincidental. While I have sat down with my children (ages newborn - 8 years) and read a couple pages, I wanted to hold off and weave it in with our home school, which I'm so excited about!
Also, there is a nice website with further activities - Church History ABC's .