I cannot do baloons because of a latex allergy but paper lanterns would do awesome for this! Kids garden or tea party decor. Add pretty little butterflies to the balloons and see your theme come together beautifully.
Flower letters is a very simple and beautiful DIY project for a baby girl nursery. Buy fake flowers from the dollar store, letters from a crafts store (or just cut them out yourself) and glue the flowers onto the letter.
Drink Umbrella Wreath - Here is a great fun idea for a summer wreath for your front door. Get a Styrofoam wreath and stick a ton of fun drink umbrellas in them. This would be so great to put out while hosting a luau or summer swim party.
Tutorial: DIY Tissue Paper Pom-Poms this tutorial is pretty good. Use square sheets or tissue for a rounder Pom Pom. We tied the middle with ribbon and tied several on ribbon and hung them for a backdrop. Use thin tissue paper and fluff gently.