help i think i've bitten off my than i can chew

i have taken on the task of making 25 of the little elf houses so my daughters class can decorate them for their christmas project. can anyone tell me
1) can i store the gingerbread with out it getting soft as there are no ovens at the school to harden them, if so how, project is on the 19 december.
2) the kids and i made a couple over the weekend to see how they worked out but we seemed to use an awful lot of the icing to complete anyone have a recipe for icing that would be able to complete this project without running out! help!!! jo