Advice on making application for my child

We have a Child Arrangements Order in place since last year which states that nobody may cause the child to be known by a new surname. Father has no contact with children. Order allows for him to send letters, but it's essentially up to the children as to whether they wish to have contact with him - they do not. Father lives overseas. History of domestic abuse affecting myself and children. My eldest child is almost 16 and wants to change their surname - while they can apparently legally do this after 16, there seems to be a bit of a contradition as parental authority and the Child Arrangements Order lasts until 18. They also asked their school not to inform Father of where they are going to 6th Form College - the school sought advice and said they can't do that as father has parental authority until 18. Child then contacted a legal advice line who said it is best for me to make the application for them on both issues. The problem I have is that the Child Matters case stopped short of the Fact Finding, when father withdrew his case as the children had asked to be involved. He says he wants to reapply to court now that a year has passed. In his original application he accused me of alienation, so on that basis I'm worried about making those applications for my child as that might be used as ammunition to "prove" that I'm alienating (child is very resolute about their decision and approached the school without me knowing first, and has been wanting to change their name for years). I'm worried about what the possible consequences of me making these applications myself might be? Are there any alternatives?