Ask your supplier for the maximum gold thickness.  They will likely need to ask their subcontractor, but they should have the answer.  Having only a minimum thickness for gold is inadequate, but way too common.  Once you have this, you can make a better decision, but my bet is that you don't need to dip.  The dipping seems like an investment in money and lead-time that is likely unnecessary, plus adds another process to add damage or defect opportunities.  The advantage with PTH is that there is a high volume of solder to dilute the gold.  There should be no issue with dissolving it completely at typical wave solder temperature and times.  Gold dissolves very quickly into solder.  There will even be some washing off of the gold as it goes through, but you should do the gold concentration calculation without this, looking for less than 3 wt%.