CalGal,
Welcome to The Highway!
I would recommend using a children's catechism prior to the actual Apostle's Creed. The Creed is a mighty summary of the faith, originally designed as a short expression of the essentials of the faith by one being baptized, but its use assumes that one has had time to learn and study the content of its various elements, and that is what the older catechisms were designed in part to do.
We used the Catechism for Young Children based on the Westminster Shorter Catechism. This would certainly be age-appropriate for both your girls, especially if they have not been catechised prior to this.
Of course you will want to tailor the teaching to their particular level of understanding, but the essential thing is to get the basic facts of the faith into their minds now; the processing of those facts will be much easier for them if the doctrines are presented in the order of the catechism. So with your 5-year-old's confusion as an example, she needs to learn about the nature of the one God, prior to the Trinity, and then the facts of the Trinity prior to the Son of God becoming man as Jesus, etc. So, for example, the AWANA teaching that "Jesus" is the Creator--incorrect since Jesus did not exist until conceived in Mary; it was the Son of God, who, with the Spirit, but obeying the will of the Father, created, thus Creation is attributed initially to the Father--will be corrected.
Sorry I don't have a good link right now for that Catechism. I have one, but it lacks scriptural references which would certainly be appropriate as you teach your daughters. Maybe someone else could provide a link?
