Be rest assured. When I was 60 and my wife was 54, we undertook an arduous tour for 27 days including Badri, Kedar, Gangotri, Yamunotri etc apart from Gaya, Varanasi and Vaishnavo Devi etc. We took our mother in law who was at that time 78 year old. Ponies are available at the Gowri Kund. Air at top is thin but if they don't have any major problems, they can easily have Darshan. After Kedarji, you may go to Badrinath also. Formerly, we used to walk to Badrinathji from Joshimath. Nowadays, single way buses do go.
Pray to Him and go and have Darshan.