The butterflies that are attracted to your annuals are not going to be the cabbage white which will happily lay its eggs on any brassica it can get near enough to. I see no reason not to plant them, though it is a little early in the year yet.

Calendula - (old-fashioned Marigolds) are pretty and have insect pest deterrent properties, I believe.

Calendula are good because blackfly love 'em, so they choose to go on those instead of on your crops. Also pretty. I used to grow Clarkia, really like those, most insects aren't keen cos they're double flowers. Other than that, Godetia I loved, but they have a shorter flowering period; Helichrysum bracteum, commonly known as the strawflower - cut the flowers at the right time and they keep for years, I still have some in pot pourri from 20 years ago, bit battered now! I also liked old fashioned statice (annual Limonium), another one you can cut and keep in a vase as dried flowers for a year or so. You don't see these growing much any more, any of the ones I've mentioned.

Edible annuals include Nasturtium (black fly love these too) and Amaranthus.
You could also try some ginger, Liquourice plant and chives even.
Summer flowering varieties of Salvia elegans is another thought.