Montana Kev,
Seem to be experiencing a slow start at the office this morning, at least that's my excuse for checking out the brats instead of doing something productive. Hmm.. that didn't come out quite right.
Anyway, I realize I didn't actually get to the main point on the previous post, but Dr. Bob did.
You will want to keep a real close eye on the weather and consider the forecast on the radio as just a general suggestion of what might be in store. The main thing to look out for is the wind. It can come up quickly and unexpectedly, especially in the spring. The wind can get channeled around by the canyons and even when you are in fairly open areas can make its way around the compass like an amusement park ride. 10 or 20 mph forecasted winds can easily turn into 40+ mph from any and all directions if there is any kind of front coming through, or just because it decides to blow. Just be sure you're on a real good anchor or tied down very well to the beach.
Be careful, be safe and you are going to have a great time. Lake Powell is a magical place.