Thanks for the information and hints folks. Yes, we are invited the the actual wedding ceremony as guests and on follow-up reception. The bride is fairly westernized to the point that vietnamese is her third language.

One clarification came that the reception and most activities (don't know about the ceremony) will be held at the place called Do Son. Googling reveals that it is a resort place for the domestic tourism - highest review score for all properties there is 6 with an advice - 'reset your expectations to zero'. Oh well.

Regarding transportation options again - so, how one can avoid get scammed? It is not the money ($10 more won't make me poor) - I just really do not like to be taken advantage of and fit into 'stupid clueless foreigner' category.

Beer or any alcohol drinking - hope this can be avoided due to medical reasons.