They look good!
I'm sure they'll be fine Alice, pumice or no. Weather in Texas seems to be pretty mellow this time of year, and despite all this discussion's focus on how best to grow them, sempervivum are pretty tough plants.
I don't use gravel at the bottom of my pots, I've read that it actually does the opposite of what most folks think. Instead of quickening the drainage process it actually slows it by creating larger pores at the base of the pot, and because water molecules like to stick to each other, those larger pores actually encourage the water to remain higher in the pot for longer. In this theory, you want your largest particles on top and the finer ones on the bottom. Though "gravel mulch" is a piece of this theory that is widely accepted, continuing the water wicking pattern of largest to smallest from top to bottom is rarely practiced by gardeners below the top layer of substrate. Once again, not a big enough deal to go tearing apart your well thought out and attractively executed planters, but something to consider for the future. I've heard some pushback to this theory, but it seems to make sense to me. Scientifically, the model is likened to a rectangular sponge full of water, the sponge is obviously full of small pores, but the space around the perimeter of the sponge can also be thought of as a set of larger pores, the widest of which is the flat long side of the sponge, if held so that the largest side of the sponge faces the ground, it will retain water longer, however if the sponge is held sideways so the side with the smallest area is facing the ground, the water will run through it more quickly. Thus the finer pores being at the bottom of the pot would cause a faster movement of water by wicking it out of the soil molecularly. You don't want to clog the exit's by using particles so fine water can't pass through them, but short of this the theory holds true. Often I mix a separate soil for the bottom layer of my pots with more sand and less gravel, not that it's an absolute necessity.
-Sol