Make drop flowers one day in advance. Prepare royal icing following recipe directions. Tint portions dark rose and light rose; reserve some white. Use tip 224 and 225 and rose icings to make about 21 swirl drop flowers for each treat on parchment paper. Use tip 3 and white icing to pipe dot centers. Reserve remaining white icing. Let dry overnight.
Prepare whoopie pies following recipe directions. For red whoopie pies, tint batter red. Bake and cool whoopie pies according to pan package directions. You will need two pies for each treat.
Assemble pies. Prepare filling following recipe directions. Use tip 2A to cover one pie with filling. Sandwich second pie. Roll edges of pies in desired sprinkles or sugar.
Make fondant hearts. Tint fondant rose. Use fondant roller with purple rings to roll out fondant 1/8 in. thick. Use medium Cut-Out to cut heart.
For lattice heart, use knife to score lattice lines, 1/4 in. apart. For sugar-covered heart, brush top with piping gel and sprinkle with pink sugar. Use piping gel to attach hearts to top of whoopie pies.
Make heart vine whoopie pie. Tint reserved white icing green. Use tip 3 to pipe outline heart in green. Use icing to attach flowers in groups of three to five.