Ashton Court is a possibility, but shuts at 8:15 (not a problem for a 100, but...). Busy as well.
Street parking in Southville, or try Cumberland Road - and finish with a pint outside the Cottage.
(from Cumberland Rd, get onto the 'chocolate path' by river heading west. Turn L onto old railway bridge, cycle path to Clanage Rd, then Kennel Lodge Rd, through Ashton Court.)