I don't believe you can transfer points from a Marriott account to another:
Points can only be transferred from one account to another at the time of ordering a reward in increments of 1,000 points. To do this, a point transfer form must be requested from the Marriott Rewards customer service office. Include both account numbers on the form, the number of points to be transferred and the reward to be requested. Return the form with the signature of both account holders. When you’ve completed the form, please fax it to 801-468-4033 and the points will be transferred and the reward issued.
However, that is not necessary since if your Dad had a lot of WN points, he could use them to purchase you tickets.
To the best of my knowledge, there is no direct way for your Dad to transfer his Marriott points to Southwest. There are indirect ways, but those are usually at bad transfer rates.