Is there any way to get my land hermit crabs to liven up a bit

Keeping your humidity up and making sure that you have the proper requirements for them is the best, and if you do try givng them things to climb on and lots of extra shells to try on and extra room to move around, here is a site that has hermit crab requirements so you can double check yours.
http://exoticpets.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=exoticpets&zu=http%3A%2F%2Faboutlandhermitcrabs.com

try a little house-warming . that really gets them hopping

Nope. Do not force them out of their shell either. You could hurt them. Hermit crabs are very quiet animals. They are not supposed to be active.