I don't think there will be place to get water closeby.

This could be a problem for grandmothers. Do they realize this? Windy is good for alpines. While alpines need excellent drainage, that doesn't necessarily mean they are xeric plants and do well with little water. And remember, most all perennials will not look finished the first year.

Would everyone turn their noses up if the one farthest from the water source is cactus and succulents? Even without the cactus part, sedums and sempervivums(Hens & Chicks) are varied enough to provide good diversity in size, color and shape. Rock placement would be integral in such a design.

You could use shorter forms of upright sedums like Black Jack, garden variety spreading sedums, Sedum caudicola(or S.c. 'Lidakense'), small leaf forms, Sedum 'Angelina', tiny cobweb type hen & chicks(Sedum arachnoides), ones with large rosettes, and they come in many colors. Sisyrinchium spp. (Blue-eyed grass) would go well with these too. And no fertilizing for this container.

BUT, practically no perennial garden is as floriferous as annuals. A major thing to consider.

As far as "regular" short perennials that might be good:
the dwarf forms of Balloon flower, Sentimental Blue
Blue-eyed grass (Sisyrinchium sp)
Basket of-gold Aurina saxitilis(Alyssum saxitile)or A.s.'Compacta
Pussytoes (Antennaria sp.)
Alliums
Dwarf Goatsbeard (Aruncus aethusifolius)
Low Pinks (Dianthus sp.)
Dwarf or spreading forms of Baby's Breath
Pasque flowers (Pulsatilla sp.)
Thyme (Thymus sp.)
Low spreading veronica's like Waterperry

Don't forget the rocks. They should be arranged so they look 'natural' rather than a haphazard mishmash. Don't be afraid to go as big as possible when it comes to rocks.