"Vadiar" is a derogatory term for wasting time instead of working or doing something more productive (like skipping school, or spending all day long in the beach, or drinking, or on tv, or using drugs), no one in Brazil usually call his friends to "vadiar" together, nor a capoeirista will say something like that when he wants to play ("jogar") with someone. The problem is the author used this word in a way that doesn't make sense in Portuguese. The English counterpart makes sense, since the "mestre" is calling him to have a fun time, but not in a "wasteful" way. Of course, author did this because "vamos vadiar" is a capoeira song (just google it).