We have birds of paradise and pigface ( aussie rambler) trailing over the wall ,near our pool in full sun and they are doing well.

star jasmine would look stunning under the magnolias, lush green and gorgeous perfumed white flowers.

myoporum, it's a ground cover that does well in full sun, foliage comes in a few colours and has small. usually white flowers

Hi Mel! The plants mentioned above are great suggestions. You could also consider local natives such as Native Wisteria (Hardenbergia comptoniana), Ruby Saltbush (Enchylaena tomentosa) or the Thick-leaved Fan Flower (Scaevola crassifolia). Good luck!