I agree with much of the advice given. We have spent lots of time camping out in the Oregon dunes. It can be lots of fun. It can also be a sandy mess, and an expensive one if things don't go well.
One suggestion I would make, especially if you haven't driven on sand, is detach the trailer and drive around w/ just the SUV before bringing the trailer out onto the sand. Sand is different everywhere, and even can vary from trip to trip depending on moisture content, winds, stuff like that. There were times we would easily make it to our preferred spots, others when it was like a truck pull trying to get the RVs out there.
Anyway, without the trailer, you'll get a sense of how loose/deep/easy you can move around in the sand. For example, find out if you can start from a dead stop easily, or is it a struggle? If your TV is struggling alone, you know your trailer will get you stuck!