His details are on the birth certificates, which are needed to apply for the passports, so not giving his details isn’t an option.
OP I would suggest you seek some legal advice, because there is a lot of inaccurate advice on this thread.
E.g. nursery would not be able to refuse to let him take them as he has parental responsibility. Unless there are legal steps in place he has just as much right to collect the children as the OP.
You need to be pragmatic here rather than be panicked into thinking that he is going to steal your children as people here are so often keen to suggest.
There are some things in your favour but there are also things which you need to consider.
In terms of access, if there is no reason to believe he is a risk to the children then he is likely to be granted some access in the future, and at some point that is likely to involve the children being able to travel to the Netherlands.
The Netherlands is part of the Haigh convention, so this isn’t the same as e.g. a parent moving to certain Middle Eastern countries where if the children are taken there is a high likelihood of never getting them back.
your best bet here would be to take control. So tell him that he can apply for birth certificates on the .gov website if he needs them. Then go and see a solicitor in regards to sorting out a proper access schedule, with a view to his seeing the children here for the foreseeable due to their age, and this can potentially be amended as the children get older, if this is necessary.
That way you’re seen as being cooperative in the best interests of the children, and you’re the one who is being proactive in regards to maintaining their relationship with their father.
it gives you the upper hand because you’re the one essentially suggesting the access routine, and this does put you in control. Whereas if he applies for access first then he is going to be the one making the demands while you’re the one playing catch-up in order to maintain control.