You're so welcome. As far as
the bearnaise, I have reheated it. In fact, I make a double batch and use it again the next day. It is tricky, however. I would suggest that you do it over hot water, in a double boiler with the pan above not touching the water. Not on the stove though unless you have a 'keep warm' element on your stove; that would be ideal.
Alternatively, you could measure all the ingredients in advance and make the blender version on the spot. With a blender, it's very simple. I think the important thing is good fresh tarragon and good shallots.
I use a recipe by Bocuse. I like it, but it is not a blender version. I love blender Hollandaise though. It is SO easy and foolproof.
Also, with the salad, I have made it in the morning, stacked it, removed the stackers and just left it on salad plates in the frig, covered with saran. Because of the stability of the cheese, it holds its shape well. I then just added the mesclun at serving time and a little vinaigrette. That worked fine. I massage the proportions a bit to get ultimate cinema out of the layers. It pays to show off the white layer.
Hope it goes well.