From Dehradun you are looking at a long highway day toward Guptkashi / Sitapur / Sonprayag, then a local jeep or trek. Anyone selling a “drive to the temple door” is not telling the truth.
Vehicle choice
Innova Crysta if comfort and elders matter. Bolero if you want the traditional yatra workhorse. 12-seater Tempo if the whole family must stay together. Self-drive is possible for experienced hill drivers; most families should take a chauffeur.
Timing
Start before dawn from Dehradun if you want a same-day arrival at the last motorable point. Better: a night at Guptkashi or Sitapur. We quote multi-day packages on /car-rental-kedarnath.