1. Get a grandchild for them ASAP.

 3.If i were you i would buy a desktop computer and hook it up to the TV and bookmark web links so it would be easy for them to access any movies, "aastha" channel , Nepali TV, Even any religious program from all over the world.

4. See if you have a Nepali neighbors around you. Try to establish a good relationship with them and invite them for dinner once a while. This would help your parents meet new faces and enable them to visit the neighbors by themselves. Even inviting coworkers to dinner might help.

5. Volunteering is not a good option because of the language barrier and our parents will be reluctant to communicate with people from here. 

6. Try to see if your community resettles refugees. Bhutanese refugees who share exactly same culture and language as us would be best for your parents. See if you have these refugees resettled in your area.

7. Take them in a long drive (at least more than an hour of driving) every other week.

8. Download food recipes written in our language and ask them to give a shot when bored.

9. Visit to a local park in the evening with parents.

I know you have to invest so much time and have to take care of them like kids. But they are your parents. Thats exactly what they did to you when you were young.