Many rhododendrons will do well with lots of sun, but will struggle with too much heat and dryness. Striking a balance between the two is often difficult. Full all day sun in NC, unless you are high in the mountains or very close to a lake, would very likely be too much for most rhododendrons. Morning sun and afternoon shade would be much better. Scintillation and the Roseum varieties are vigorous adaptable plants, but even they would likely struggle in all day sun.

Sandy quick draining soil is a good start, but you need to check the pH to make sure it's acid enough. Any amendments that are acid and improve the water holding capacity are good. Manure based ones like Black Cow and spent mushroom compost should be used with caution. They are often too rich in nitrogen and not acid enough. Conifer bark would be better. Mulch is important, but you're going to have to water frequently in their first years after planting.

Thanks for your advice. I think that we'll only do rhodo's in the morning sun and afternoon shade. Hopefully it will be O.K. to plant them by first of May. I've read that actually fall is the best time to plant. What's your opinion about this?

There are two, at least theoretical, advantages to fall planting. Usually there is sufficient rain to make watering less of an issue. Cooler fall temperatures should also make establishment easier. Both of these factors would apply more to hotter climates.

Today's pot grown rhododendrons are often not all that easy to establish because of the peat-based planting medium and the frequently pot bound roots. The rootball needs to be teased apart, soaked if dry and watered with a slow trickle at the plants' base throughout the summer. To my mind, having the long spring/summer season for the rhododendrons to become established is better than going into the winter not knowing for sure if the roots are sufficiently moist. There's also the danger of stimulating late soft growth with fall planting. As long as you're willing to provide the water, I think spring planting is the better choice.

There are some rhododendrons that are known for doing well in full sun. My rhododendrons are in full sun.

Sun Tolerant Rhododendrons and Azaleas

Some of my best are A. Bedford, Annah Kruschke, Belle Heller, Boule de Neige, Cadis, Chionoides, County of York, Disca, Dora Amateis, English Roseum, Gomer Waterer, Nova Zembla, PJM, Ramapo

A subset of these are those that are good for sun and heat:

Rhododendrons and Azaleas Tolerant of Sun and Heat

Mulching rhododendrons is always important, but a good mulch is even more important in sunny locations and in hot climates. It helps keep the roots cool.

The following are sun, heat and cold tolerant:

'Aunt Martha' (-10F), 'Blue Jay' (-10F), 'Blue Peter' (-10F), 'Boule de Neige' (-25F) , 'Cynthia' (-15F), 'English Roseum' (-25F), 'Myrtifolium' (-15F), Nova Zembla (-25F) and 'PJM' (-25F).

For extremes in heat such as in the US Southeast, there are some R. hyperythrum based hybrids that are very tolerant of heat. The do best in some shade.

Heat Tolerant Rhododendrons

Good Luck!

Here is a link that might be useful: How to grow rhododendrons and azaleas