I couldn't care less about your cake dilemma but I am really bothered by your relationship with your sister and your husband's comment about her.
Like, lady, you have bigger issues to worry about than a kid's birthday party.
lol
oh ye I was thinking about that too... I mean their relationship is a little strained because she could have directly said that to her sister... but, ah it's okay, brothers and sisters do not always have to get along like peanut butter n jelly :p