While President Obama was pushing his health-care reform over the weekend, First Lady Michelle Obama hit New York with their daughters, Malia and Sasha, and her mother, Marian Robinson. The family stopped at Dylan’s Candy Bar Saturday and saw a performance of Blue Man Group at the Astor. Because the Obamas took the VIP “house seats,” Phil Donahue and Marlo Thomas were relegated to the balcony. On Sunday, the Obamas brunched at Mesa Grill before taking in a matinee of “Memphis” at the Shubert Theatre. Then the gang enjoyed a private tour of the Empire State Building, nibbled on sweets at Magnolia Bak ery in the West Village and had lunch at the Russian Tea Room yesterday afternoon with about 12 girls.