Regional events calendar says summer fun is in full swing…   By DENNY DYROFF, Staff Writer, The Times   Most area residents are familiar with Longwood Gardens (Route 1, Kennett Square, 610-388-100, www.longwoodgardens.org) and much of what it has to offer. However, many have enjoyed the site’s beautiful gardens and fountains during the summer in a daytime setting only. This year...