Quick answer: Decide which family names and ceremony terms must appear, whether both languages live on one card or separate inserts, who needs print versus digital, and which wording has final approval from both families.
One card or separate inserts?
A single bilingual card works when the wording stays concise. Separate inserts are better when ceremony details differ between guest groups or when one language would make the main card visually dense.
Family names are not a literal translation problem.
Vietnamese invitations may foreground parents and family roles more strongly than many Western invitations. Decide whose names appear and in what order before layout.
Keep live logistics online.
Maps, shuttle times, dress-code changes and RSVP status are easier to maintain digitally. Print should carry the stable formal invitation; digital handles information likely to change.