I will be traveling with my husband, son, daughter-in-law and infant grandson in Germany. We are flying into FRankfurt and they will be flying into Ramstein AFB. We would like to take a train to another city on the Rhine for a several day visit. Hoping to not spend too much on train fare. Definately want to take a boat excursion on the Rhine . Any suggestions on cities to visit or where to go for inexpensive train fare and boat fare would be appreciated.