That kind of stuff will be ok, though expect a bit of attention from the locals if you are in say a miniskirt in town, you would get less wearing shorts. vest-tops, are perfectly fine.
Down on the beach, pretty much anything goes, the poor Egyptians have seen it all before.
Remember the Sinai is a desert and it will get a bit nippy at night in January. I find a fleece ideal (over a t-shirt or shirt)... or maybe a sweater... denim jacket that kind of thing...
Have fun!