Hi Catherine
You are in luck! They are both buried together at St Beuno's Church in Llanycil, Bala.
The gravestone is in Welsh & reads:-
In Memory of Margaret, the wife of John Griffiths, Bala who was buried on the 21 March 1848 aged 55. Also in memory of her husband John Griffiths who was buried on the 20th March 1861 aged 76.
If you enter the cemetery from the main road, the grave is to the left and above the first path but before the second path closer to the boundary closest to Bala.
Indeed Richard was baptised at Capel y Park, the address given is Parc Bach & the mother was from Llanuwchlyn parish.
Also William was born on the 14 April 1822 (same address)
Hope that's of help
Alwyn