Jelly drops have an excellent marketing campaign. Before deciding they’re the solution, look at how much water they actually have and how much sugar.
Nutrition, fluids and mobility wise. I’ve taken you at your word on money no object. Also a selection that can mix together.
Meals - M&S ready meals, Charlie Bingham or Cook. Higher budget and higher nutritional context ingredients than many others. Tastier than Wiltshire farm foods. Then add smoked salmon / hot smoked salmon, cheese and biscuits, and proper puddings. Custard, rice pudding, ice cream (mini Hagen daz tubs, mini magnums).
Then outings for meals. Book a taxi twice a week to pick them both up and take them somewhere they like for coffee and cake / lunch. Pick a friend up on the way if helps. There will be a local taxi driver whos happy doing frail and doddery. By booking it, it’s a commitment rather than a casual thing that relies on your dad nagging to do. Even if means first few weeks getting an agency carer to go with them as a helper. Generally you won’t get a person, but talk to agencies and get a feel. Some will have a small pool they will work from for each client.
Physio - great idea. Ideally home visit so can also eyeball the set up, make tweaks and leave them both with their homework. Second visit of chair based exercise person, or a PT (there are one who specialise in elderly). Then add a regular massage therapist. Get moving and aches fawned over.
Drinking wise - get clear on what the mobility and urinary continence situation is. You’ll know is theres no toilet around that’s easy to use, you won’t drink lots yourself. But you make it up later. If toileting is always hard for her, or struggles with leakage the logical solution is drink less.
Mobility - hair appointment once a week? On a day with nothing else on. Drink at the hair dressers. Preferably with biscuits. Get hair dresser on side. Also, going out forces the getting up and moving a little bit to get there.