My family and I are travelling from Copenhagen, Denmark, to Basel SBB with interrail pass friday night to saturday morning. From Basel we need to take a local train (S6) to Schwarzwaldstrasse in Lörrach, Germany, saturday morning, where we pick up a car. Can we use our interrail passes or do we need to buy a local train ticket? And which ticket do we buy for two adults and two children, age 6 and 8? Thank you!