Upside down pineapple cake HELP!?

I'm planning on making this for my mums birthday but she has a particular cake flavour she wants - vanilla. So i've been planning on making her an upside down pineapple cake but, i know how to do the pineapple stuff, i'm just wondering if it's ok to use a different cake mix in there or if you have to use the one it says to use. I don't want to ask her because it will ruin the surprise. So please, do i follow the recipe, or is that just a guide for others who don't have a cake mix already planned?