Sure you can put candles in strawberry shortcake. They may get a bit of whipped cream on them, but who cares? You can like that off the candles.  I have a July birthday and am not a particular fan of birthday cake.  My fantasy is candles in a big, round, center cut slice of watermelon – so that you have the "appearance" of a birthday cake and the sweet refreshment of watermelon in July.