If you're really to do maids duties and the emphasies is on doing the chores and not on wearing the dress, then i'd go for the low heels.
And i would definitely not go and buy them in a fancy shoe store, but in a store where "normal" housewifes buy their "normal" everyday shoes.

However, i think if i were your Mistress, i wouldn't want to miss watching you buying those shoes. And of course you had to try them on before you buy them