For an affordable family day out that offers lots of fresh air and some spectacular scenery, why not visit one of Kent’s open gardens? The National Garden Scheme has more than 100 gardens opening across the county this year, with some offering open days during the Easter holidays. We’ve picked just a few of our favourites – and the best part about them is that kids can visit for free. Cobham Hall, near Gravesend Take your family on a trip to the filming location for Channel 4’s Junior Bake Off. The famous tent pops up on the lawns of this boarding school to film every season, so you might reco…