Hi there!
I am a certified vet tech, so hopefully I can help you out. First of all...I would highly recommend doing a few "trial runs" with the dogs. If they are not already seasoned travelers, you may be surprised in the difference of how they travel for a short trip (say to the vet's or the groomer's) versus a much longer trip.
The dogs are for sure going to need several potty breaks during your trip. I would consider every few hours for quick potty breaks, and then make at least one or 2 of your stops a good long break, with time for a leash walk so they can really stretch their legs and burn some energy.
If they are not good travelers you could ask your veterinarian what he/she recommends as a sedative for travel. Sometimes just an OTC Benadryl will work to help sedate them a little. Again...ask your vet, and do some trial runs first.
You should consider crates for the dogs while traveling if space permits, or seatbelts if you don't have the space for crates. This will keep them safe and secure and also your family. God forbid you get into an accident...your unrestrained pets can actually become "flying debri" and injure someone in the car. Horrible thought I know...but it does happen.
The kitty should also be in a crate for sure, but it should be a large crate. Enough room to place a small litter pan, and a bowl of food and water. One tip I got recently was to get one of those bowls that clip onto the door of the cage, and freeze water in the bowl the night before your trip. The water will melt enough throughout the trip to allow the cat to lick at it, without causing a mess from a spilled bowl of water.
Sedatives for cats are not as easy as dogs. There are a lot of medications out there that are highly toxic to cats. So again...do a trial run first, and if your cat is miserable (howling, crying, trying to escape the cage) then speak with your vet about a sedative. Don't give him anything over the counter.
Hope this helps a bit. I would call your vet's office for any further recommendations, but as long as you have the space in the car, and the ability to take multiple rest stops, you should be fine.
Oh...one last thing...make sure your animals have collars, and ID tags. Be sure to put your phone number on the tags. You may want to consider getting them microchipped as a permanent means of identification.