We have a rowing machine at home- it doesn't mean we use it regularly.
If you want to lose weight- you have to change what you eat. It's as simple as that. But also as complicated- we (as a society) still don't
really know the magic trick to losing weight, and then there's the whole emotional and social aspect to eating which can't be ignored.
But- what you really want isn't to be thinner, is it? It's to maintain your health, and the stuff you need to do for that doesn't
necessarily mean you need to lose weight.
Does it matter to you that you ride sloooooowly? [I know it matters for me, but that's because I'm vain, and used to be faster than I am now, but that doesn't mean it matters to you]
Being more mobile requires more strength and more flexibilty. More strength comes from lifting things, and more flexibility comes from bending.
Your walking and cycling is probably all the aerobic stuff you need.
I'd recommend pilates (you're a middle class white woman, you should be doing it already
)