Chicken thighs (dark meat) are a "little" more moist than breasts (white meat). This it true of any poultry (turkey, pheasant, cornish game hens, etc.) in terms of a dark meat vs. light meat comparison. So, if "roasting" poultry, just be sure that you add a little moisture to white meats. The moisture can be in almost any form: water, chicken (or any) stock, wine, or you can simply add a tiny bit of extra fat, such as a pat of butter or drizzle of oil.
The BEAUTY of a slow cooker is that you can cook almost ANYTHING successfully, without a specific recipe. Just add what your family likes -- and be experimental. The slow cooker will preserve the natural juices because it cooks SO SLOW. You really do not have to add moisture to the breasts to be successful in a slow cooker unless you intend to cook them a really long time. They will substitute completely for thighs in any dish.
Here are some things to try: Cook the chicken alone in the cooker by simply adding about 1 teaspoon of olive oil to the cooker and turning the breasts in the olive oil to barely coat the surface of the cooker and the chicken pieces. To add variety you can top each piece with +/- a tablespoon of ANY sauce, such as: BBQ sauce, lemon pepper marinade (I like Lawrey's), marinara/spaghetti/pizza sauce, Worcestershire, orange juice, soy sauce, etc. -- whatever flavor you like! In addition to the sauce you can choose vegetables (and some fruits) depending on the flavor and combinations you wish to end with. For instance, add: onions and bell peppers; quartered red potatoes; sliced zucchini; or carrots. If we want a slightly oriental flavor, I add pineapple chunks (or mandarin oranges) with the bell pepper and onions and serve over rice. I melt a little jack cheese and parmesan on the chicken that I cook with marinara sauce and serve it with some type of pasta (spaghetti, rotini, shells...). You can also experiment with spices, like rosemary, thyme and/or paprika on the plain oiled chicken; ginger, curry and even cloves and cinnamon on the fruity versions; or basil, oregano and/or parsley on the tomato based dishes. We like garlic (powder or diced) with everything. For variety, you might try various cuts of pork (chops, boneless rib meat or pork loin) with the fruits, like applesauce, fresh apple chunks, raisins or Craisins, fruit juices or apricot jam.
Since you work full time, I recommend cutting the veggies at night and storing in the fridge in a ziploc. Then you can dump it all in the slow cooker in the AM in minutes - and have dinner waiting when you get home. [Hint: cooking time will depend on the quantity that you cook in the crock-pot. Because you cook for five, I would think that any of the above suggestions with sauce (plus any additional veggies) could gook on the low setting for +/- 8 hours. If you were cooking a lot less, like only 2-3 breasts, and no veggies, the meat would cook in +/- 4 hours, consequently it would need some extra moisture (sauce and/or veggies) to prevent drying out during an all-day cook.]
One of our favorites is to splash milk (about a cupful) over the oiled chicken breasts and then sprinkle the whole dish with salt, DRY flour (1/4 to 1/2 cup) and lots of black pepper. Once it has cooked, it comes out somewhere between chicken with cream gravy or chicken & dumplings. My grandmother used to cook chicken this way in the oven in a covered casserole (or roaster) and it is a family favorite!