Soldato
Definitely Cathedral and Quays as staying there. Think heard Chedworth Roman Villa in the mix. Dad loves his Roman stuffDepending on where you are staying the following are worth doing:
Lido in Cheltenham
Pitville Park in Chetenham
Painswick Beacon for a walk
Leckhampton hill (Devil's Chimney) for a walk
Rboinswood hill & park
Brewery quarter in Cheltenham
Gloucester Quays
Gloucester Cathedral
If you go bit further afield, the birds of prey place near Newant is excellent
Plus you're on the doorstep of the Forest of Dean and lovely towns/villages around there
Plenty of pubs along the River Severn, plus lots to do in the Cotswolds.