Most pilgrims to Kedarnath also visit Badrinath — the "Do Dham". The practical order is Kedarnath first (the harder trek, done while fresh), then the motorable Badrinath. Allow 5–7 days from Haridwar: drive to Guptkashi, trek to Kedarnath, return, then drive via Chopta/Ukhimath and Joshimath to Badrinath, with Mana village as a bonus stop.
Register once for the full circuit, carry layers for both valleys, and keep one buffer day for mountain weather.