It’s 4/20. Do you know where your children are? SEE Waist Down What: Soho’s Prada rises from the ashes with skirt installations by Rem Koolhaas’s firm, AMO. Why: For further “research,” hit the registers. When: Mon.-Sat., 11 a.m.-7 p.m., Sun., noon-6 p.m. Thru May 31. Where: 575 Broadway, at Prince St. (212-334-8888). HEAR Shakespeare Birthday Marathon What: In the name of the bard, Robert Sean Leonard, Estelle Parsons, Marcia Gay Harden, John Turturro, and others do readings. Why: It’s all in the articulation. When: Sun., 3:30-7:30 p.m. Where: Symphony Space, 2537 Broadway, at 95th St. (212-327-3399). EAT Chinatown Food Festival What: One- and two-buck dishes from teahouses, cafes, and iconic dives. Why: A lovely day for a little wok. When: Sat., 1-6 p.m. Where: Chinatown, Canal to Worth Sts., Bowery to Baxter Sts. BUY Lolli by Reincarnation Sample Sale Party What: Summer dresses, were $250, now $75; leather sandals (in 60 colors) were $130, now $40. Bites and sips will be served. Why: We represent the Lolli-pop kids. When: Fri. & Sat., 10 a.m.-midnight; Sun 11 a.m.-9 p.m. Where: 85 Stanton St., b/t Orchard & Allen Sts. (212-529-2030). Find Outlet Sale What: Alice + Olivia tops and bottoms, C&C tees, Chaiken pants, plus Paper Denim, Diane Medak, and C Label at 50 to 70 percent off. Why: One hundred percent shopping satisfaction. When: Thurs.-Sun., noon-7 p.m. Where: 361 W. 17th St., b/t Eighth & Ninth Aves. (212-243-3177).