Children learn best from exhibits involving lights and colors, which means you can either take them to a children's museum or let them rub their eyes too hard. Teach wee ones safely with today's Groupon: for $21, you get a museum outing for four to The Discovery Museums in Acton (up to a $42 value). Members, teachers, and children younger than 1 are admitted for free, and all visitors receive free admission the first Friday night of the month. Visitors should note the museum’s regular hours and dates of extended hours and closings before planning a visit.

The Discovery Museums promotes children’s learning with creative, hands-on exhibits inside its Children’s Discovery Museum and Science Discovery Museum, both located on a single 4.5-acre campus. At the Children’s Discovery Museum, tykes age 0–6 explore themed rooms scattered throughout three floors of a historic Victorian house, which is guarded by ghostly 19th-century butlers. Young minds are stimulated as kids engineer a train track, explore the foliage of the Tree House room, and scramble over a shipwreck at the outdoor Bessie's Cove during warm weather.

Children of all ages and adults unravel mysteries of the natural world inside the 8,500-square-foot Science Discovery Museum. Math and engineering concepts smartly spill from an 8-foot water vortex and silently sluice through the air as ninja balls bounce up to three stories high before disappearing into thin air. In the SoundLab, future music-producers can experiment with beats, and the Dream Green exhibit teaches Earth inhabitants how to give the planet a big green smooch. Before visiting, parents can check out the grown-ups’ guide for previews of museum exhibits and tips on doing science activities at home using just a pipe-cleaner and an interstellar vortex.