Lightning Network Unidirectional Transaction
All channels on the lightning network are bidirectional, even if they are only used in one direction.  However, this does not mean that both parties contribute to the funding transaction.  In fact, in the current spec only a single party contributes to the funding transaction.

That said, your scenario is not a good use case for its own channel.  The overhead of a channel for the purpose of paying for a weeks worth of coffee if probably not worth it.  Most likely you'd simply route the payments over an existing channel and through other hubs and channels.