Karle leni, Bhaje leni near Lonavala

Lal Mahal, evening show at Shaniwarwada, Pune University, IUCAA, Giant Meterwave Radio Telescope @ Khodad, Kesariwada, Vishram baug wada.

Kamshet - the Paragliding Paradise in India - http://www.flynirvana.com/visit/kamshet.html

I have taken many international visitors to climb Singhagadh Fort (of course thats not a 1/2 day trip) and they seem to have enjoyed it a lot and in most cases wanted to do it again :)! though is may not be cultural/historic in some senses, its surely fun! The fort is indeed cultural/historic and has interesting history attached and adds to the fun at the end of the short trek...

Chokhi Dhani is a good place if they aren't already doing the tourist circuit and visiting Rajasthan :) Similar to Sanskruti mentioned earlier in this thread, but bigger and better in my opinion. For a more traditional Maharashtrian cultural experience, Abhiruchi is a decent option as well.

Sanskruti Garden Restaurant is a nice place to visit. They showcase many cultural and heritage skills of Indians. You will find Mehndi, Jyotish, Kumhaar, different folk dances, etc. Also, the food (snacks & meal) is good. Sometimes in the evening, they play orchestra and Gazals, too. It's 4 to 5 hours of good fun.

Kids would find the Joshis miniature train museum, Kohrud of interest (http://minirailways.tripod.com/)