This is what you get when you click "Check availability" on the previous page.

Notes:

1. There are four options shown, but two Dauer-Spezial fares are sold out (no longer available) for those times. To search for available times, click "Change ... journey", but those fares would be more.
2. In this case, the lowest fare is a Sparpreis 50 (RT, Saturday night stay, 3 day advance purchase) fare. With this fare, the first person pays half (½ of €178 RT, €89, and each additional "Mitfahrer" (co-traveler), up to four, pays half of that, €44,50. Since the under 15 children are still free, the total is €89 + €44,50, = €133,50.

Below is what appears when you click on "Purchase" for the Sparpreis 50 fare.

Notes: You can select from two options, Seat reservations and Delivery method.

1. Under Seat reservations, you can purchase this ticket with seat reservations. They would cost €4,00 for your entire family for each directions. Both trains on the outward connection, FRA to Würzburg and Würzburg to Munich would be reserved.
   Or, you could purchase just the ticket, without seat reservations.
   Or, if you already have tickets without reservations, or you have a railpass or an annual pass, you can purchase seat reservations only. Note that seat reservations only cost €8, twice as much as if you purchased them with a ticket.
2. You can choose to receive your tickets "online". In which case they will send you a .pdf file which you can print at home. You will need to pay with your credit card, which you must have with you on the train for identification.
   Or, you can choose to have them mail you a paper ticket at home for a €3,50 mailing fee. I understand that this takes about 8 business days to the U.S.