I'm definitely not a fan of putting everyone in the same thing (ie: white shirt and jeans) and think that the outfits selected should show personality, but still coordinate nicely and translate well in photos.
For mom, a sweater with a sweet pattern like hearts is feminine yet trendy, and pairs nicely with dark skinny jeans and a pair of leather ankle booties. For accessories, since it is winter, grabbing a light weight scarf is a nice idea, and here I've chosen a mint color to pick up on the holiday colors.
For a toddler boy (or school-age, ack! Mine's 4.5 now!), I really love this preppy look with a vest over a simple white collared shirt. Add in a pop of color with some bold jeans!
For Dad, bring in that pop of color with a sweater (optional: add a collared shirt under neath), and pair with simple dark jeans. I love the shoe option here for Dad's, particularly the stripe detailing on the heel. They add just enough pattern, but not so much that it is intrusive.
For baby boy, while they will outgrow these clothes the minute you put them on, they're pretty freaking adorable. Jeans and a collared onesie, in neutral tones like the rest of the family. Since it can be hard to find things like bandana bibs or accessories in the right colors to accent and coordinate with the rest of the family, look for things like handmade rattles (LOVE that moose!) and their favorite blanket (or a new one!). These items will keep them both entertained, and look great in photos!