My few cents -
Roads are good now so no need to worry. Trust, you have mixed up between Rackcham and Karcham. Have stayed at those hotels at Rackcham and Kalpa and both are good specially food, seems Jisthu Ji have sent you the offer. Cost is bit higher, 35K could have been a good deal. You can even minimize the cost by opting for Sedan class vehicle in lieu of SUV. That will save minimum Rs.500/day on A/c. of car hiring. Plan A looks better any day and yes, Chitkul with layer of white is probable.
Travelled just a month back from Delhi to Kalpa during Diwali. Roads are excellent now. Post Wangtoo i was driving at a speed of 60-80Km/hr. On the way back reached narkanda in 6 hours. narkanda to delhi - standard 10 hours drive.
Day temperature would be comfortable, don't require to wear woolen but once sun sets temperature drops drastically. So pack enough woolen stuff and cover him appropriately at night.
You can look at my trip report (in signature) for some idea about weather condition, snow levels. I'd advise you to steer clear of Karchham as the notable attraction is a large hydroelectric plant. There's usually some maintenance carried out and it generates fine dust. A better bet is to stay in Chitkul (check my TR for hotels etc). It will be the coldest place you'd visit on your trip, but perhaps the most scenic.
Also you will require woolens in April. I needed them in May first week!
Thanks for replying...
As I spoke to the driver, it may happen, Chitkul may be unreachable that time, if roads are not cleared. Otherwise, I will stay in Chitkul, as I missed it in 2010 :)
You may visit this thread
It may be helpful.