A cycle helmet needs to do two things: protect your head, and be comfortable. For a perfect fit, choose a helmet with a dial adjustment. To keep the kids safe, pick up a helmet with their favourite cartoon characters and a quick-release buckle. Vent holes help keep your head cool, so look out for a vented design if speed's your thing.
A full-face helmet provides better protection for thrill seekers who like to try a jump or two. Mountain bikes and BMX bikes can take a bit of a beating, so need to be kept in good condition. Regularly check and inflate your bike tyres, and invest in some bike storage to protect them from the elements.