Abstain from aluminum usage.
Iron is fine, as long as it's not oxidized (rusted) -- so keep your iron cookware well oiled for protection against unwanted chemical reactions!
Discussion
I actually don't recommend cast iron because elemental iron, as opposed to heme, is extremely toxic to the body.
Same reason I avoid elemental aluminum.
There's no free lunch.
Some women have trouble with stainless because even small amounts of elemental nickel can be problematic.
On balance I think it's the best of the options.
A glass kettle is great if your stove/situation supports it.