My children and I are learning Koine Greek using Mounce. We also have a number of other books and resources (I’ll mention them as I go).
Some printable sheets I have made to help my children learn the Koine Greek Alphabet. (updated 20/4/09)
If they also learn to write the name of the Greek letters ( on the sheets) they will learn the Greek capitals and also they can practice sounding out Greek words reinforcing the letters sounds.