Who comes first in a blended family?

I have two little girls (4&6) from my first marriage and I recently remarried. Both my kids and husband demand a lot of attention from me (as they should). My husband also has a little boy from a previous marriage but we only have him every other weekend. My husband and I were supposed to go out on a dinner date last night and my mom was supposed to come and take care of the girls. (We have date nights once a week) However, about an hour before we left my 4 year old spiked a fever and said she felt unwell. I told my husband that we couldn’t go to dinner tonight because I wanted to stay home with my daughter. He seemed to get upset when I told him this and then proceeded to tell me that spending time with him should be my first priority now that we are married. I could’ve easily left my sick child with my mom but that’s not the kind of mom I am. My girls are my priority. I am a mother first, before anything else. He never had an issue with it before. I love him so so much, but kids come first, he’s a father himself so I assumed he knew that. Am I wrong for putting my babies first?