My children have been involved in the Catechesis of the Good Shepherd for several years and I have completed the training for Level 1 (3-6 year olds). The program is based on Scripture and the Liturgy and is very solid in doctrinal content. Being Montessori based, it is very hands-on and allows the children to make discoveries about the faith themselves. For example, they learn the paraple of the Good Shepherd and gradually (with the guidance of the Catechist) come to realize that Jesus is the Good Shepherd and we are the sheep. They learn about the Real Presence from hearing the words of Jesus in the Bible. For this reason, you won’t necessarily find doctrine explicitly taught, but it is present nonetheless. It gives them an opportunity for them to develop and deep and abiding relationship with the Good Shepherd himself, and a love for His Church.
The international headquarters in Rome has developed a variety of presentations and each presentation includes (for the Catechist) a statement of the doctrinal content that is being presented to the child. I have never been the slightest bit uncomfortable with any it. If you want to learn more, try reading “The Religious Potential of the Child” or “The Good Shepherd and the Child”.
I have only experienced the program that my kids are involved in, so I don’t know how much it varies. Many of the families involved in our program belong to the local FSSP parish. We have Mass (OF) as a group several times a year and the Mass is always reverently celebrated, but the tone for that is very much set by whoever is running the program.