Decorating for different celebrations is a really good way to get children involved, and this bunting is so easy that as long as a child can hold a glue spreader they can join in.
First you need to cut some heart shapes from red and pink cardboard. I drew a heart free hand, but an easy way to make a heart is to use the shapes from Microsoft Word or similar and print them out. Then collect together an assortment of appropriate collage materials in red and pink - scraps of tissue paper, paper napkins, bits of lace or ribbon, coloured paper, sequins and so on.
Let the children decorate the hearts with plenty of glue. Then when they are dry string them together with some coloured ribbon or string, hang up and enjoy!
You can find more heart themed ideas for young children here - Heart Crafts and Activities