Colleen,
fixing an American dinner should be no problem. You will be able to find beef in supermarkets quite easily, and prices are not always as horrendous as reported.
The same applies generally to having dinner at a restaurant. The
general rule is: the more traditional (tatami, sake etc), the more expensive.
I wish you and your family all the best in Japan, enjoy your stay, I am sure you will definitely have a good time!