It is fine to clean them with air, its just something to be conscious of.
For example, if a fan has a max speed of 1600 rpm, and you spin it with an air blower manually at 3000 rpm, you could risk damaging it. So it depends on the fan and the force of the air being used.
Compressed air cans don’t provide enough pressure for this to be a problem.
If you use some of the tools mentioned previously, you may need to hold it further back or hold the fan still while you clean it.
I also will usually get in there with a lightly damp cloth after cleaning with air in order to get some of the remaining dust out. This can be tough depending on the type of fan. Obviously a PC case fan can be taken out and cleaned properly. A laptop fan may not have that option.