I want to bring my iPad to a beach to do some reading while on vacation. I am concerned about sand getting into its ports and causing damage. Obviously water would also be a concern, but I am not planning on taking it in any water. Does sand propose a significant threat and what can be done to limit the chances of a problem occurring?
Yes you can, but there are some aspects of the environment of the beach life that need to be controlled.
I would probably have a Chef Sleeve or two with me and bring an umbrella or shade to control the light and direct heat. A ziplock bag also works if you don't think the closer fitting sleeve is worth spending money on. Depending on your beach some or all of these concerns may be disregarded, but I tried to cover the common beach scenarios.
Other than that - keep it cool, heat yourself up and enjoy your iPad on the beach.
I'm going to expand my comment to @bmike's answer into another answer to this question for future seekers. Consider buying a Kindle for beach use.
Please understand that I applaud the desire to use the iPad for reading on the beach. As I see it, I paid real money for the tool, and if I'm not going use that tool as I want to, I shouldn't have bothered. That being said, there are certain risks and inconveniences that accompany this (and all) decision.
First, @bmike is correct about the danger that heat presents to portable electronics. That being said, my experience has taught me that if you're going to read with the iPad, you'll either seek or make shade. That risk is manageable. You'll also want to take proper care to keep your iPad cool when you're not using it. Options include a bag in the shade or (assuming the iPad is appropriately protected) in the top tray of a large cooler. Please, don't toss it down into the ice.
Perhaps a higher risk comes from flashing an expensive piece of kit on public beaches, both here and abroad. Assuming you're not going to stuff it into a waterproof case whenever the urge to take a dip strikes, or carry it with you as you and a loved one stroll hand-in-hand along the beach, the iPad presents a juicy target of opportunity to those who just weren't raised right (or for whom an iPad sold means eating tonight). It also brands you as a rich tourista and perhaps paints an even bigger target on your own person. (I trust my spanish-speaking friends here will forgive the slight as none is intended, it's just the linqua franca for much of my beach travel).
Add this risk to the inconvenience or as some would say, utter unreadability, of the LCD screen in bright sunlight and I can make a reasonable argument for leaving the iPad back in the room, and tossing a (relatively disposable) Kindle into my beach bag.
I use an OtterBox Defender case to protect my iPad in harsh environments. If I'm using it as a "chart plotter" on a small boat or kayak, I also put it into a waterproof map bag (along with a desiccant packet) that I got from an outdoor store.
For occasional use, you can also protect the iPad within a 1 gallon Zip-Loc™ bag. (Again, I'd add a desiccant packet if you're using it in a humid environment). I keep a Zip-Loc in my go bag for this purpose.