Is there specific wording we should use for the self-declaration form for Disclosure under the Childcare Act?

As there is no statutory requirement to have a self-declaration form I don't have a template I'm afraid. To a certain extent it will depend on the context of your school.

For example the guidance says, 'It’s not necessary for schools to ask staff to complete a self-declaration form to obtain information about whether a staff member is disqualified. Where schools decide to adopt the approach of using a self-declaration form, it’s important that the questions posed in the declaration are relevant and limited to the requirements of the legislation, (for example cautions or convictions for a relevant offence, or whether a child has been made subject of a care order due to the care provided by the individual). This may mean that schools may not be able to use a generic self-declaration form for all employees, for example a teacher working solely with year 5 children (age 9 and above) would be exempt from this legislation. Schools should inform their staff that when responding to questions about their cautions or convictions, they do not need to provide details about any convictions that are not relevant to the childcare disqualification legislation.'

The guidance is here: https://www.gov.uk/government/publications/disqualification-under-the-childcare-act-2006/disqualification-under-the-childcare-act-2006