With a short pool, you are limited, especially if you have an efficient flip turn. Since you are a beginner, I don't think that is a problem (Not a knock, just a fact. Flip turns take lots of practice to be effective).

I would take a pull buoy with you and concentrate on form drills. As a beginner swimmer in a very technique driven sport, this would serve you the best, as it's hard to get effective aerobic work in a short length pool. I would recommend single arm drills, sculling, and concentration on early vertical forearm (EVF) and maintaining a high elbow through your pull.

Although you describe yourself as a beginner, 1:40 for 100m as a sustainable pace means that you have decent fitness and decent form already. I generally regard 2:00/100m sustainable pace as the break point, in that if you can achieve that pace, you probably don't have any glaring stroke flaws holding you back. Not to say there aren't improvements to be made, but your stroke isn't really hindering your progress much.