About options for desert tours below text is an explanation about the 4 main desert options that I can suggest you.
Of course there are so many other options for desert tours. On the other hand, if I was in your place , I select Maranjab desert ( No. 3 ) in Kashan city and Mesr desert ( No. 2 ) in east of Isfahan province:
1- Varzaneh desert in east of Isfahan: i don't have any special idea about Varzaneh desert. I was there 1 night and it was interesting. But it isn't depth of desert. The most important point about Varzaneh is that it is near to Isfahan and located en route of Isfahan to Yazd cities and you can reach there by 2 hours driving.
2- Mesr, Garmeh and Tabas in east of Nain city: is one of the most famous deserts of Iran after Shahdad desert.
my best recommendation about Mesr village is walking to a reedy ! near Mesr village in depth of Lut desert, a village surrounded by sandy dunes, and set your tent up beside the reedy and stay overnight there and watch stars.
You can reach to the reedy with a short walking in sandy dunes -2 hours- from Mesr desert and watch sunset in heart of central desert of Iran.
In Garmeh village visit salt lake, hot spring lagoon, palm - grove, Sassanid castel and accommodating in traditional cottage in Garmeh village and tasting local food.
There is a traditional deserty guesthouse, Ateshoony, in Garmeh village . there are some local houses in the region that introduce their selves as Ateshoony house because of its fame. And mpst of foreigner travelers aren't familiar with true Ateshoony gursthouse !
drive to Garmeh village (or Tabass city), visit depth of desert with its wonders (salt lake, hot spring lagoon, palm - grove )
After Garmeh village drive to Tabas city and visit Golshan garden inside city and Morteza Ali fountains. 2 kinds of hot and cold water are exiting from walls of a strait and flowing in the strait and at least in long of 300 meters the don't mix together because of their difference in density and flow rate.
http://seeiran.ir/چشمه-آبگرم-مرتضی-علی/
I think 3 nights is good for this region.
3- Maranjab desert ( east of Kashan city ):
You can drive there in 1.5 hours from Kashan city and stay overnight in a old caravanserai in depth of desert. The caravanserai isn't luxury but you can stay inside its traditional rooms.
There is a salt lake and also you can visit the highest dunes of iran in Maranjab desert.
4- Shahdad desert as the hottest point of our planet in southeast of Kerman city:
You can visit Kerman city + Mahan garden + Bam and Rayen ancient citadels + Shahdad desert and Sirch village as a combination desert and culture city sightseeing.
You can visit them in 3nights/3days.
Gandom beryan is the hottest point of World.
www.untoldiran.com/kerman/lut%20desert.shtml
Its Kaluts ( nature Sandy cliffs ) are beautiful.
untoldiran.com/kerman/shahdad%20desert.shtml
You can stay overnight in Shahdad desert camp inside arbours was made by leafs of palm tree. ( of course inside your sleeping bag ).
But a wonderful matter is Sirch village near to Shahdad desert that has snow even in spring and its ski resort in winter is famous in the region ( less than 1 hour ). This village located between Shahdad and Mahan cities.
