For the most part, their baptisms are valid. That is assuming that whoever does the baptism actually uses the Trinitarian formula “in the name of the Father, Son and Holy Spirit.” If other names are invoked (a typical example is “creator, redeemer, sanctifier”) then it would be an invalid attempt at baptism.
I would caution here that validity is not the only relevant question.
Even though there is only “one baptism” (just as we say in the Creeds) we are still baptised into whatever would be the relevant community (Catholic, Anglican, Lutheran, etc.) as a practical matter. Since you just stated that you are in RCIA, another question to ask yourself would be that if you believe in the One Holy Catholic and Apostolic Church, then why have your children baptised into a different ecclesial community? i.e. Anglican, or any other for that matter? Is the connection to the school more important than the full membership and full Communion which is the Catholic Church which you are now seeking for yourself? The validity of the baptism is just the starting point. It’s not the final question.