Our son has a great relationship with our helper. I think it is only natural that he feel attached to her as much as to us, since he spends most of his daytime with her. I feel sad, definitely, that neither me or my wife are staying at home, but our weekends are therefore purely meant for quality time with our son. My wife also reduced her work to 4 days a week, so that she can spend more time with him.
All-in-all this seems a good balance for all members in our family, although more would always be better. Our son is happy both when he sees our helper and when we come home. He also hardly cries when somebody leaves the house for a while.