I found a picture that shows the lantern centerpiece idea. My own interpretation will use a couple moss covered mounds to pick the flowers into. Since the wedding date was moved to april, theoretically the flower arrangement should become easier.
Lantern centerpiece 
Here are the flowers available for April arrangements:
Allium
Artichoke
Alstromeria
Babies Breath
Bells of Ireland
Boronia
Bird of Paradise
Blue Lace
Calla Lily
Carnation
Carnation, spray
Chrysanthemum varieties (poms and daisies)
Cherry Flowering Branch
Cosmos
Daffodil
Delphinium
Eucalyptus
fillers assorted (babies breath, misty etc)
Freesia
Forsythia
Garden Roses
Gardenia
Garlands
Gerbera Daisy
Greens, assorted (smilax, sprengeri, tree fern, etc)
Heather
Iris
Larkspur
Lavender
Liatris
Lily, asiatic
Lily, oriental
Lily of the Valley
Lisianthus
Mint
Muscari Hyacinth
Matsumoto Asters
Monte Casino Asters
Mum Daisy
Nerines
Peony
Phlox
Protea
Queen Anne’s Lace
Rosemary
Ranunculus
Rose Petals, Freeze-Dried
Rose Petals, fresh
Rose Wedding Bunch
Rose sweetheart/spray
Star Gazer Lily
Assorted Lilies
Scabiosa
Snapdragons
Solidaster
Statice/Misty
Stephanotis
Stock
Sunflower
Sweetpea
Tulip
Veronica
Viburnum
Waxflower