On the heels of a major Wyeth exhibition at Kansas City's Kemper Museum, Christie's and Sotheby's in New York are offering twenty-two works by N.C. Wyeth, his son Andrew and grandson Jamie, with a combined high estimate of $12.6 million. Sotheby's also has Childe Hassam's exquisite "The White Dory, Gloucester" on Thurs. while today Christie's sells a Sargent portrait and Edward Potthast's pleasant "Bathing Beach--Low Tide" ($800,000 - $1,200,000)...