Yes, they will be allowed. But how would they communicate, it's a big question.
You may check this video out for Switzerland travel, https://youtu.be/OslsFGWUtng
You can engage an agent to apply for their schengen visa which includes Switzerland and other places in the European Union. But communication will be a big challenge if they can't speak in English, unless they're taking a package tour.
Hi! For applying for a Swiss Visa, you will need to submit a visa application to the Embassy of Switzerland, either personally or through a verified travel agent. You can then track your visa application. Following is a list of the documents you need to apply for the Visa: 1. A completed Switzerland Visa application form.
2. Two passport pictures that comply with the Switzerland visa photo requirements.
3. A valid passport. Along with photocopies of current and previous passports/other travel documents
4. Medical insurance that covers your entire stay in Switzerland.
5. A cover letter that explains the reason for going to Switzerland.
6. Flight itinerary or proof of booked flight tickets.
7. Proof of accommodation in Switzerland.
8. Proof of civil status.
9. Evidence of paid Swiss Visa fee. Your parents will be allowed entry to Switzerland even if they do not speak English. It would be advisable that you pre-book a travel agent/guide who knows both English as well your parent's preferred language. Otherwise, travelling and sightseeing may pose a big problem. You can check out these trips, destinations and holiday packages for more information on what to do and where to go in Switzerland.