I'm in the same position but on the downhill side of your situation. One child, almost done with college, a lot of $$ in UTMA.
For many years I have given this much thought and am a contrarian to many of the pros on this forum. You really can't "transfer" money from a UTMA. Once a UGTMA always a UGTMA, even when in a 529. However, since we have only one child and my sibling's children do not have a pressing need for college money, I just leave a paper and computer trail on when and how much money is moved from a UGTMA to a 529. In otherwords I don't go about setting up a trust in the 529-because I don't see a need.
Since 1)son is in college, 2)son is filing 1040 for div,int,capgains; Is there a need to do a 529 if he is paying zero to minimal taxes? You may want to do some forward looking thinking and perhaps liquidate some of the LT appreciated securities and place the proceeds in a 529 because of GWB's tax perference of reduced taxation on LT and dividends. If you have losers, then they can offset the gainers in the UGTMA.
Personally I'm not a big fan of 529's for someone who is in-college or very near college, because security markets can change very rapidly and perhaps to the detriment to yours/his finances.
I pay attention to the taxes paid, unrealized gains and loses, and flexibility more than the the type of investment used, fees paid, and name on the paper.
We also have three 529s so that I can easily segregate UGTMA money and new money. I came to the same conclusion as you have.
Suggest you get a good tax and investment professionals and double check their thinkings using commericial tax and financial programs.
I'd be careful in putting all of the $11grand in a 529 from a UGTMA without careful tax, risk, and expected use analysis.