Hi Catriona!
First a request: Due to a board software update (actually, two!) I no longer am able to use the auto-resize program I had for avatars so you need to reduce yours (otherwise right now, the whole screen on my large browser window is nothing but Jasper, as cute as he is!! :lol:
You can find out how to do this here:
http://www.cavaliertalk.com/phpBB2/viewtopic.php?t=1671
Second:
A four hour journey should be easy for your pup. For safety reasons, he should be in a crate, *never* on a lap or raoming free. In even a minor collision he would become a very dangerous missile and could actually break the neck of another passenger in the car. A minor collision could also throw him straight into the back of the front seat and break HIS neck. Also being crated will keep him from getting dangerously underfoot near the driver or otherwise distracting the driver. And, you want him very safely confined for any rest stops as they can squeeze out a door and be gone forever in an instant. Being crated also is much less stressful for the dog than being overstimulated or frightened by car movement and also lessens the chance for carsickness, which is common in young dogs not very well acclimated to a car.
Alternatively you could get a safety seatbelt harness from any good petshop but I have my doubts that seatbelts would actually note the weight of the dog and lock properly in a collision. Also they can get twisted up in them especially if overexcited. So a crate is the best option especially at this age for a pup. He'll probably just go to sleep.
If he is whiny just ignore him and he should settle. You can also cover the crate in a sheet or towel (make sure he can get air though) -- the dim light is calming for stressed dogs.
Put a couple of interesting chew toys in the crate for him. You will probably want to stop every 60-90 minutes for a weewee stop, when you can also give him some water, and walk him a bit. Before anyone opens any doors, you should gently let him out of the crate and fasten his lead to his collar or harness. Be sure no doors are opened til that lead is safely clicked into place and som eone has a good hold of the other end of the lead! Rest stops like this are a common way that dogs get lost after bolting into an area they do not know so be extra careful.
I recommend not feeding him the morning of travel. This makes it far less likely that he will be carsick. He will be fine getting a late meal. If you feed him, you will likely see his entire meal return in a form you don't care for. :lol:
Bring along some paper towels, and probably an old towel as well, plus some poop bags. I fill an old water bottle for water and bring a little plastic container for serving water when travelling.
Have fun! Most dogs love the gentle movement of a car and settle pretty quickly. Oh yeah, I also recommend calming music like Lyric FM for the drive. Booming rock music is pretty stressful for a dog in a stressed situation. Calming music is known to lower animal stress levels. 8)