Just when you thought you had the baby burrito mastered, the swaddle unravels — once and for all.Good-bye, wrap. Hello, sleep sack.Make the transition to swaddle-free sleeping as easy as Sunday morning (before kids) with the latest from Aden + Anais. The beloved swaddle maker fashioned its famous cotton muslin into crib sheets.Just like the company’s all-purpose blankets, the muslin bedding gets softer every time it’s washed. Elastic edging makes for a secure fit over the mattress, and a wide weave allows air to circulate, helping regulate baby’s temperature and keep him safe.The sheets come in soft, solid colors (gray, pink, blue) and delicate patterns (owls, stars, dogs) that lull even the youngest resters into a deep sleep.Just like a burrito but without the indigestion.Available online at adenandanais.com, $30-$40.Photo: Courtesy of Aden + Anais BLOOMJapan Spring Opening Day CelebrationWhat: Make mini dioramas, fold origami paper into cherry blossoms, and watch a Kabuki performance. Why: Say sayonara to winter. When: Sat., 11 a.m.-5 p.m.; origami, 11 a.m.-2 p.m.; dioramas & performance, 2 p.m.Where: Arthur M. Sackler Gallery, 1050 Independence Ave. SW (202-633-1000); Freer Gallery of Art, Jefferson Dr. SW, at 12th St. (202-633-4880). Participation is free.WATCHEnvironmental Film FestivalWhat: Prepare to be inspired by the lineup of nature-themed flicks (better still, nearly all the movies are free). Why: Future do-gooders get their fill of family-friendly selections.When: Thru Sun.Where: Locations, schedule, and tickets online at dcenvironmentalfilmfest.org. Adults and teens, free-$16; children, free-$12.SAILKite FestivalWhat: Try out 18th-century activities, watch puppet shows, and cross your fingers for a strong gust of wind. Why: Your tech-savvy tot needs some old-fashioned fun. When: Sat., noon-5 p.m.Where: Gunston Hall, 10709 Gunston Rd., Lorton (703-550-9220). Adults, $10; children and teens 6-18, $6; children 2-5, $2; under 2, free.