Talk

Can't speak specifically about lisbon (sorry!) but I took my dad for a last holiday abroad to Barcelona. In retrospect he was in early/ mid stages of dementia, which is not you r situation, but here are some things that helped:
Being liberal with hailing taxis as soon as he got tired.
Building visits around things he was into - history, churches, restaurants. I researched restaurants in advance by using the website Chowhound and posting questions/ soliciting recommendations. Avoided very noisy venues (not always easy in Spain!).
Lisbon can be hilly when you start going up to the higher neighbourhoods. There are tramways/ funiculars that go up the steep streets- maybe research where the funiculars are in advance.
Museums will have loos, and cafes of course. From memory the Gulbenkian museum is very good.
I am glad I took him on that hoilday, even though it was exhausting (for me) at times. Good luck.

It’s very hilly in Lisbon! I’d recommend a tram tour.

Lisbon is indeed very hilly. Go for the tram tour and use the metro a lot.

They have those little moped car things all over the place that you can get for a tour - some seemed perfectly safe with seatbelts etc!!

Trams can get really busy

You can arrange tours quite easily with mini can firms too I believe. We didn't in the end but it seemed quite reasonably priced.

Ditto the hills in Lisbon. The best sights are on hills or in hilly areas - and not necessarily on public transport routes. I think you should consider using taxis for some of your visit.

I must admit that Lisbon wouldn't be first on my list for someone with limited mobility.

Thanks all, my goodness there were some steep slopes, but we managed using taxis (relatively cheap) and a tram to Belem which is flat.