There are a lot of simple hacks that you might try to get rid of the smell in the finished dish, which involves adding small amounts of herbs or spices etc. But of course, it needs to ensured that no-one will have any adverse effect with the additives.
1) Add lemon juice (fresh squeezed is better) and some ground black pepper near the end of boiling. This is a classic combination.
2) Add Bay leaves and whole black peppers in water when you start boiling.
3) Add sage/thyme during the boiling.
Just keep in mind one thing: The smell and taste capability of many elders are diminished, and the plain boiled chicken might not smell too bad for them. and they might be more interested in avoiding anything that might upset their stomach than a better-smelling chicken.