2 hours is just right amount of time to spend a tour in Petrosains

How about something less involved, like picnic.

I co-own edu company that involves bringing kids outdoors. Many times we had this kind of similar 2-hour situation - too long to wait out, too short for any meaningful activities.

So what we typically do for this is, go to park or somewhere pretty, sit down and make sandwich. We would just bring those 1kg kewpie tuna and scrambled eggs and many other sandwich ingredients (we always have this in stock since we regularly do hiking and sandwich is our staple for this activity).
And then we will give the kids liberty to invent their own sandwich to eat. Positive feedback every time.
Kids tends to behave nicely when presented with meal. They learn what work and what not work in food prep, and you get to teach about food waste. Everyone happy.