Allium 'Globemaster' - Alliums are nicknamed "Ornamental Onions." - The flowers (which are spheres formed of a whole lot of tightly packed tiny flowers called florets) can be softball to volleyball sized on stems up to three feet tall.
I love colorful foliage plants. They also are perennials and would come up here after year. I think this is a beautiful idea to plant these hosta type plants under a tree with all their different colors
Angelonia Serena Mix - this isn't in your landscape plan but Angelinia might be a good "filler" option for your patio beds while the other plants grow in. Or it could replace the lantana if you prefer.