I usually wait and buy most of my plants in May because I never know when to start my seeds indoors. This handy little chart lets you know when to start seeds indoors as well as when to plant outdoors.
7 Tips to Start Seeds in the Winter. This would be something cool to do with your kids. It really makes them feel proud when they see something they helped create. When you and the kids harvest the garden, they will be extra proud and excited that they helped to "make" the food and may make them more likely to eat their creations; win, win. This starts in late Feb to early March!