My first thought of a fast growing and seemingly ever blooming groundcover was
Dune Sunflower (Helianthus debilis) but that is fairly common and the yellow color won't work well with the pinks/purples. How tall do your Adenium and Kalanchoe get? I thought those were fairly tall, like 12", 14" or more?
Something with white blooms would look great with pink/purple and the blue pots.
