I think the answer is that there are no guarantees of club suites on any route as equipment gets switched in and out. I'd be inclined to look at AA flights instead, or First if within budget.

As to special assistance at airports, yes BA do this and it's usually OK, there can be some delays disembarking at Heathrow. My wife uses it. There is no differentiation based on class of travel though I think you can purchase special special assistance at T3 which is where AA mostly flies to/from.