Before leaving the subject of flower shows--if they are of interest--Google "flower shows" and shows all over the country are at your finger tips. Click "flower shows 2010" and check out Chicago--March 6-14; Portland Me.--March 11-14; Chicago and San Francisco--March 24-28 and Newport RI--June 25-27 to name a few.
There are boat shows, car shows, etc., some of which should appeal to apathetic aging parents. If music and theater hold more appeal, check out:
Tanglewood in Lenox, Mass. The Boston Symphony presents outstanding musical programs during the summer--indoors and outdoors. Located in the Berkshires, the surroundings are beautiful and it's very popular with older people. Bring a picnic if you wish, but do check the weather forecast.
The Shakespearean Festival, Ashland, Oregon. This is a favorite summer destination, now in its 75th year, and the quality of the productions is well known. Ashland is a picturesque town not far from the California border. While the pear trees in Ashland are the delicious variety used in Harry and David's famous fruit gift packages, there is also a well-remembered, disgusting-tasting mineral water, Lithia water, that comes from an underground source. Dad stopped to make us drink some from a fountain in the park anytime we drove through Ashland when we were kids. Said it would help us live to 100. He died at 94. Hmmm.