Hmm..it sounds to me like you may have just a tad too much on your plate at the moment (no pun intended). Here's a few suggestion that you could do....
1. Don't do diets right now, or even think of the word diet. Just focus on buying more fruits, veggies, and avoiding processed foods..(organic, natural, you name it....use turkey meat in place of beef as it's leaner for instance, and add more veggies...I generally do this with chili's, and you can't even tell it's turkey!). I recommend checking out a few cookbooks from the library that you could make a healthy meal from one to two nights a week. In addition, work on moderation....do portion control with your food, even doing smaller plates if necessary.
2. I too am a college student, and I try to use the stairs when going to my classes instead of the elevator. Unless you're running late for class, do this as often as you can. You can also get a pedometer that measures the number of steps you take in an average day..the ideal number of steps is 10,000 per day.
3. There are some gyms that offer daycare within while you're working out. Of course, this involves having pay for membership, so this is entirely up to your money situation. Since you have a supportive husband, why not schedule time for yourself to go the gym while he watches the kids? (Some colleges have gyms on campus that you can go to....if I remember right, it was generally "free" for full time students (not sure about part time) since it was covered in their semester bills..you'll have to check into yours)
4. One thing I do recommend...is cutting out soda pops. I used to be a huge coca-cola fan, and gradually cut it out of my life. I did lose a pound or two from this, and don't miss the sodas.
5. Keep in mind, all this will take time and don't expect changes overnight. Think of it more as a learning journey as you go along. Plus, winter tends to bring about the blues, and especially with the holidays looming, everyone is worried about bills and how they're gonna pay for everything. Don't let it stress you out. You can even have your husband watch the kids while you're taking a full hour bath for relaxation.....