all my kids will/have my surname until me and my partner marry.
you can always change your little ones surname if/when you marry and you change your name.
i would have found it very hard if my kids didn't have my surname. even though me and my partner are very close and nothing would split us up (or so i hope), i still wanted them to have my name.
mark understood it was something i needed/wanted to do and was happy with it, cause he knows that when we marry, we will all take his name.