Tet (Lunar New Year Day) for 2017 is on 28-Jan-2017. Vietnamese tradition calls for the celebration to start a few days before and a few days after the Lunar New Year Day. The government sets the Tet holiday period each year. For example, Tet (Lunar New Year Day) for 2016 is on Monday 8-Feb-2016, and this year's official holiday period starts from Sat 6-Feb through Sunday 14-Feb.
Beside the official holiday period for the locals, Tet is also a heavy travel period for Vietnamese overseas returning for family gathering or vacationing. Their travel pattern of course is not the same as for the locals. Usually folks overseas will start their homeward migration 2 weeks before the Lunar New Year Day and leave 2 weeks after that date.
My suggestion is for you to plan your trip in late Feb/early Mar 2017 to avoid your concerns. Arriving before Tet would be during the period of Christmas and New Year and you would get into a similar but not as bad situation.
Hope this helps,