Greenwich river cruise is good but does get cold on the water for an hour.
There are river boat restaurants which are quite touristy and in good locations.
It depends a bit on how mobile they are. I’d keep it all pretty central.
Royal Academy has some great exhibitions and is not too big, check in advance.
Ronnie Scotts already mentioned is a great spot for jazz, also central.
The South bank is great in the summer for a walk, this also leads to vinopolis (previously mentioned which is a wine experience)
Shakespeare’s Globe is also in the area but you probably want seats if your folks are 60 but thye might prefer a different show.
Restaurants – what do they like? there is literally anything from Ethiopian Goat curry to Indian / French fusion to Argentinian steak houses to michelin stars.
Hotels – check out lastminute.com secret hotels. I do that now when taking the missus out and you can get a great deal on 4 or 5 star hotels (<£100 for 2 people including breakfast).