Why does my bunny constantly lick us?

We have had her for a week now and she never did i at first but suddenly she started licking the other day, she will lick any bit of skin she can find, even feet, which amuses my 4 year old immensely, is this alright or will it make her ill, or is it a sign that something maybe wrong. We have 2 and they are on a diet of pellets and hay and even seem to eat the straw, they have also had in very small amounts grass, dandelion leaves and apples to begin with will add more over time.