They are a bit too small to judge, really. I do not like the one where she has two heads though!
I am just looking at your original cover http://www.lulu.com/shop/elizabeth-keimach/the-pig-child/paperback/product-22825362.html and even with the image large it's hard to tell it's not just a normal human child.
I would go no less than 12 point and possibly 14. Garamond is a great font.
Italics sometimes seem to shrink slightly, rendering text less readable, so it is not always a bad idea to increase italics by one size over plain text.
If Garamond is not available or is not to your liking, Bookman Old Style is good, and Times New Roman is also acceptable. Avoid sans serif fonts.
Also, full justification is extremely highly recommended.
I am sure that's what I said ...