Listen, we know some of you little guys hit the bottle. Sometimes six, eight times a day. We’re not judging, but that’s a lot of bottles.And we also know bottles are expensive — which is why Room to Grow supplies them to families who can’t afford to buy their own.So when the good folks there found out that BPA in plastics was risky, they did what you did — threw out their entire stock of feeding supplies with the nasty chemical. Which is where you come in.Help them refill their shelves by donating new bottles and sippy cups online at Room to Grow’s baby registry at Babies “R” Us or dropping off your extras at the nonprofit’s Back Bay location.We’ll drink to that.Room to Grow, 142 Berkeley Street, Back Bay (617-859-4545 or roomtogrow.org); online at toysrus.com.DIGWaltham Farm DayWhat: Cider-making, family-friendly volunteering, community farm art project, compost exploration, and more.Why: Get your hands dirty.When: Sat., 2-5 p.m.Where: Waltham Fields Community Farm, 240 Beaver St., Waltham (781-899-2403).PLAYMom’s & Dad’s Guide Metro South Kids ExpoWhat: Back-to-school bash with moonwalk, resources, prizes, and a raffle.Why: It’s everybody’s day off.When: Sun., 11 a.m.-3 p.m.Where: Totplex, 5 Carver Cir., Canton (781-821-0304).ROCKFall into Disco What: Cool breeze is coming in. Heat things up with the Baby Loves Disco crew.Why: Strut your stuff.When: Sun., 2-5 p.m.Where: Revolution Rock Bar, 200 High St., Downtown (617-261-4200).