The MFA’s Rienzi house museum hosted its annual spring cocktail soiree, which this year adopted a colorful Mexican fiesta theme. A mariachi band and trays of margaritas greeted the 300-plus guests, who mingled poolside and dined on a Swift + Co. spread of squash blossom quesadillas and roasted corn — all while raising more than $150,000 for the institution. ... And at the Evening in the Park event, benefiting the Hermann Park Conservancy, Mayor Sylvester Turner greeted guests and toasted the 25th anniversary of the park’s Japanese Garden — an occasion which inspired the event’s east-meets-west menu, courtesy of A Fare Extraordinaire.