The Netherlands is a member of the European Union and British Citizens do not require a visa to enter the Netherlands. If you intend to live in the Netherlands, you should get important documents, such as birth certificates and marriage certificates, officially certified (apostilled) at the FCO Legalisation Office.
The Dutch border authorities have strengthened their border controls in precautions against child abduction. Parents travelling in sole charge of their children are regularly stopped for further checks, to avoid delays, you should carry a signed authorisation form for travelling abroad with a minor, along with copies of the authorising adults’ passports and any other documents that relate to the guardianship/custody of the child.
Your passport should be valid for the intended duration of your stay.