(from an electronics manufacturing engineer - my prev. career)

Be careful with compressed air and vacuuming internals.

Moving dry air creates static electricity. Static charges, if transferred to electronic components will damage them. (ESD - Electro Static Discharge)

Moving air such as thru the nozzle of a vacuum cleaner will generate static charge on the nozzle (plastic, insulator) which can be discharged to electronics thru contact. Service techs who have to vacuum electronics have special ESD-safe vacuums to do the job. They also have ESD-safe grounded mats to put the boards on and keep components in ESD-safe conductive plastic or mylar bags until installation.

Cleaning the dust out therefore offers the opportunity to kill the computer with ESD.

I'd brush the dust off using a metal handled, short-bristle brush and use a vacuum cleaner in the area to catch the generated airborne dust. I would NOT use the vacuum nozzle directly on the board or heat sinks. (fan and grills would be ok)