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If you are putting them out as centerpieces, I doubt they will attract many Bees. Bees normally have to send out scouts to find a source of food (flowers) who report back and tell the other bees where they are. If the flowers will only be there for an afternoon, the scouts will not have much of a chance to tell anyone, even if they do find the flowers in that short period of time.

It is a flower that originally comes from the rain forests, so I cannot see why you would not be able to grow them. It may be the salt, but if you grow them in containers, you should be able to control the salt.

This article should help with that: https://www.gardeningknowhow.com/ornamental/flowers/impatiens/growing-impatiens-flowers.htm

The leaves usually turn yellow when the plant lacks Nitrogen. Perhaps water stagnates and the roots get too much of water. See whether the pot is packed with roots, if so transfer the plant to a bigger pot. If the plant is in the ground add some compost around the root.

The screening may have made it too dark for many plants to bloom there. You will want to try shade flowers, although if you tried new guinea impatiens, it may be too dark for shade flowers even.

You can also consider growing colorful foliage plants that like the shade, like caladium or coleus.