.........damn, man. Just... damn.
You're an absolute saint. Just keep cool, and remember that you love them (the fact you said you loved them like your own is the key to this whole thing).
As for a 4-year-old and a 2-year-old, there are still things you need to do to your house.
Check every cabinet below 5 ft high. Why 5 ft? Kids can climb on anything, like chairs, and get at a cabinet. You're checking for anything they could drink or eat and die from. You need child locks for any cabinet you have to keep any cleaning supplies in, like under the bathroom and kitchen sinks. If you have plates or breakables in low cabinets, move them up to a higher cabinet, and if you have anything that's not breakable- like mixing bowls, plastic cups, etc., move them down. This will help prevent curious hands from becoming destructive hands.
As for the nanny, I'd ask for a list of references. Once you get to know the person well, call their references and talk to their former employers, see what they have to say. You may get 4 glowing reports from one nanny, or 4 "meh, she did her job but that's it", regardless of how outgoing, nice, or personable they appear to you. Also, I don't know what your dynamic is with your mom, it sounds good, but I'd ask her to help you out with the nanny-choosing. If nothing else, she might be able to ask specific questions you might not think of, or she may be able to "pick up on" some of those positive nurturing qualities the nanny should possess.
Just keep asking questions- a lot of people make it up as they go along, so don't freak out.
Good luck.
