We went to the Exploratorium just last year with DS15 and he loved it, although it is noisy. Perhaps they have quieter times for younger kids? If not maybe there is a 'toddler playgroup' that organizes out of there to meet other local gifted parents who will know the local lay of the land.
www.exploratorium.edu/Back on task - did this link have any good suggestions?
http://www.hoagiesgifted.org/psychologists.htm#ucaAlso I would suggest you call Mika Gustavson,http://www.mika-mft.com/
I've met her in person and she is wonderful.
I don't know if she does testing herself, but if not she could let you know what's local.
Good luck and let me know how it's going, ok?
Grinity