M.,
Is being a stay at home Mom an option for you? For some it is, and some it isn't. Many women aren't comfortable staying home because it doesn't fit with their personality and their goals. If you can't stay home, then you do what you have to do. No matter which side of that fence you stand on, there's guilt. There's a really great Montessouri pre-school near me that I would LOVE to send my son to in September, but I can't because the tuition is out of my reach. If I worked, I could afford that. No matter what choices you make, there are tradeoffs, and whenever you think about those, you're going to feel guilty. That's the badge of motherhood.
Hopefully you are feeling confident in your child-care choice. It's going to be hard, and you're going to cry, and then you're going to go home to him, and it'll be okay. It sounds like you've cut your commute down, so that's a benefit to him in the new job, and I bet a great offer means more money! That benefits your whole family too. Just do what needs doing, and you'll see that it's an adjustment, but you're all going to be all right with it.
Jess