I'm making a rainbow cake with buttercream icing and fondant decorations for DD1's 4th birthday. I'm worried it will look great but taste really boring. The cake is plain sponge and the buttercream is also plain/vanilla flavour. Should I add some flavouring to either the sponge or the icing? Maybe lemony sponge and/or strawberry flavoured icing. Or is this over the top? Are there any other flavours that would make the cake taste more interesting?