I'll be starting a thread about ideas for fighting the winter blues soon! Like right after the holidays.
Exercise and joyful movement are the enemies of depression. Dance, playing hide and seek or tag, go for a FAST walk, or do hard physical labor-moving firewood, shoveling, etc.
GO OUT. It doesn't matter where. I love the library. If you haven't been to your local library lately, ask for a tour. Do you KNOW what's there? Vidoes, hundreds of tehm, all free, any book known to mankind, computers, information, clubs, childrens groups, craft days, contests for kids. Can't find the book you want, they can order it for you. ANYTHING!
Any childrens museums near you? See if they have a free afternoon, or ...check at the library
and see if they have free passes.
What's near you? Can you ice skate? Babe could go in one of those sleds you push, you and 7 yo coud get some exercise.
TURN UP THE MUSIC! Blare it. Sing along like crazy, have contests for who dances crazier.
Have rewards...go for a walk on a cold day, get a hot chocolate when you get back.
Our local elementary school has community sing every Friday. Everyone is welcome.