Maybe you would like to buy four kits. Then all you have to provide are the trimmings. I would suggest you get a kit for yourself so you can practice and give them some ideas. Or start cutting out pictures so they can get ideas from them. Then all you have to do is whip up some frosting and buy different candies. Buy extra as they will eat as much as they put on the houses.
I made two of them when I only had three kids and one of the was an infant. It was a LOT of work and sugar. Gingerbread can be hard to work with as the dough loves to be sticky. They were two very interesting houses. I doubt either the gingerbread boy or girl would want to live in one. Just like the trees the kids decorated over the years, however it came out, that is the way the houses stayed. They thought they were beautiful, and they were. Gumdrop shutters, chimney on the ground, and every time I had to leave their side to tend to the baby, mayhem broke out. Finally around February they agreed that the house should be put outside for the birds to eat. Their father took them finally down to the trash and buried in the bottom of the trash can.
I have to admire you for wanting to take on this task. Good luck.