Many people were caught out with thin clothing and were shivering during the boat trip. They had to stay in the cabins most of the time and missed out on some good views around the lake!
The backpack is also good for taking small snacks like pastries, bread, cookies, etc. as lunch is not till 1:30 pm and the trip starts around 9 am. If you got picked up much earlier than that then it will be a while before having a real meal again.
The bags we took were also useful for souvenirs as we opted to take the speed train back to Tokyo.
Of course good walking shoes are always best in trips outdoors. Though there was the sky gondola ride and boat rip, you still have o do a lot of walking especially around the Visitor's Centre at Hakone as it has a huge reserve/park and lots of ground to cover.
It is a good idea to pack a small first aid kit for small accidents l- band-aid, little ointment/disinfectant, etc.
Cameras - digital or not are a must
Out door gear is highly recommended- especially wind breakers as it could be windy during the cruise and the trek to the mountain/Valley of Hell.
Layering is the standard here for clothing- meaning you just remove a layer of clothing depending on the prevailign weather, then add a jacket or coat one the climate gets colder again.
Take also scarves and beanies for your family.
The Gray Line Company is the main organiser of the Hakone/Mt. Fuji day tours. Other companies also use them aside from the hotels in case you book through your hotel. You pay them directly. The hotel only rings them for you.
