I think that might just be them being not used to it. I had that problem almost half a year ago when I started running. My calfs were the only part of my body that started to struggle after just 1 km. After doing a 2 km run 3 times a week for a month it disappeared though. With some good running shoes you should be fine, as long as you don't have any other issues with how you run, which you can check up at a qualified... runguy (gyms usually have one)
Summer holidays are coming up and I thought of buying new running shoes and get ut running 2-3 times a week and see if that helps.