Valuation in these circs a difficult one, i'd give the 206 a shot, cars with this mileage through sensible use (as described) don't come up often, would be a shame to not give it a go however you value it.

My issue here is with brakes being expensive on an Aygo, that should be far from the case, they are simple as can be with cheap and easy parts availabilty, only requiring a bit of annual TLC as any and every braking system does (but seldom receives).

Presumably seizing front calipers?...the only reason these seize is neglect, properly cleaned and lubed once a year by a sensible, home or dad?, mechanic, preferably every spring when the salt has gone, they will last indefinately, friction materials cheap as chips and one of the simplest there is to work on.

Only you can answer this, but selling a car to someone you know (i.e.have to meet occasionally) can be tricky. Despite its silly low mileage, I wonder about the wisdom of replacing a 'troublesome' car with a 13-year-old one. At that age little things usually come up at MoT time. If the 206 has been kept under cover, rather than exposed to the elements, a lot may be going for it, and it should be safe to pass on to your daughter, or relatively easy to sell privately. If not, it may be wiser to sell as-is, to preserve family relations.

Unless you enjoy tinkering yourself? At least it isn't a mass of modern electronics.