Luggage allowance on Japan Expressway Bus

I've booked tickets on one of the Japan Expressway buses from Kawaguchiko to Tokyo, but note that their luggage policy states "Passengers are allowed 1 piece of luggage (total linear dimensions up to 1 meter, weight up to 10 kg, volume up to 0.027 cubic meters) per person (including luggage loaded into the trunk room)" (similar to this post). I am traveling with children and we will each have a standard airplane carry-on sized bag with total dimensions 1.22m (slightly greater than the 1m requirement). Moreover, we will have an umbrella stroller and each person will have a small backpack. I am concerned that I will be refused entry to this bus since it seems to only allow 1 item per person. Do you have any experience with this type of bus and if so how do you handle luggage? Must you use a luggage delivery service? Thanks!