Well, my kids are older this time around, but I'm basically going through about the same thing you are right now, and have been through it before when the kids were younger. I've been a SAHM on and off for several years. My kids are now teenagers and my oldest daughter has graduated high school and is on her own now too.
I'll go back to the first time I was forced to deal. My family had been through a FLOOD, a RELOCATION (because of the flood), and then WELFARE REFORM forced me to do one of four things: 1) Work @ least 25 hours/week, 2) Attend school @ least 25 hours a week, 3) Volunteer @ least 25 hours/week or 4) a combination of any of the above three.
For me, I choose the Volunteer @ least 25 hours/week because I thought it would be the most flexible with my family's situation. I was paid so much for gas per day that I volunteered. I volunteered at a local hosptial. I also received childcare assistance. It was rough in the beginning with my youngest daughter who was pre-school age at the time. She would cry from the point she left me until the point I would return. My poor babysitter, headstart van driver, and teachers. My daughter had many changes during that time that she was dealing with. She had just lost her home due to flooding, we had moved away from the only family she had really known, and then I was being forced to be away from her due to the new changes in welfare reform. But I remember the day that she made it through w/o crying and the teacher actually gave her a certificate. The babysitter (it was a neighbor) found that if she got my daughter to help her clean the house ('weep the floors as my daughter called it) and then gave her a popcycle for helping, it was something she looked forward to. Also, we would take her favorite doll with us in the morning and give it to the babysitter so that she would have something familiar at the babysitter's house when she got there in the afternoon. The adjustments came eventually...all it took was some time for all of us to cure the problem.
I have since been divorced and my kids are older. I've been at home on and off a few times since then, and I'm once again getting ready to re-enter the workforce in the near future. This time the adjustment is going to be more difficult for me I think that my kids though. Raising teenagers as a single mom brings a whole lot new and different problems. I'm just glad I have a boyfriend that will be able to help me some with the girls for the pick up and drop offs from school. He works nights, so hopefully we will be able to manage the upcoming changes that are about to come our way as I'm also considering going back to school for my Master's Degree as well. I've also been looking for mommy groups and single mom's groups in the area for support as my support group around me is next to nothing right now. The problem with the mommy groups is that most moms have younger kids which meet for 'playdates' and my kids are teens and don't fit into the group or have the same level of entertainment for the kids.
You will do just fine. Just be sure to find an employer that is understanding of your situation and is flexible enough should you ever have to leave early some days, especially in the beginning when everyone is adjusting. Also, don't overdue it yourself and allow yourself time to adjust as well as the kids. And don't focus too much on your job and your kids that you forget about your husband. It's a delicate balance that has been increasing the divorce rates because woman are having such a difficult time finding the balance being women, wives, and mothers. Good luck to you. I'm here should you ever need someone to talk to.