Make sure to bring hats, waterproof gloves and layers. While the base of the mountain can have mild temperatures, once you are on the glacier it becomes chilly pretty quickly. Bring along water and snacks as there is nothing accessible once you leave Breheimsenteret. Be sure to stop in the restroom before you get on the boat. Otherwise, nature is all you have.
Children must be 6 or older. The family hike guides meet you at the bottom of the glacier portion of the mountain, not in the parking lot. It is about a 1 hour hike over fairly difficult, rocky terrain to get to the glacier. Be sure to stay to the left, cross the bridge and follow the orange cones. The red dot path along the right side of the mountain will not give you access to the glacier.
Your tickets aren't time specific, but during July and August the hike leaves 4 times per day with bus service running daily. Aim for the earlier hike, so if you miss it, you can catch the next one. In September and October there is only one tour daily, otherwise private tours are offered.
July and August are the prime months to visit, with relatively mild weather. The weather becomes pretty harsh in October and would not be ideal for young children (or anyone besides die-hard winter lovers).
Tickets can be purchased online through the Nigardsbreen website, arranged through Norway in a Nutshell or purchased at the Breheimsenteret Glacier Center.