Re: Cake Smash!
I've got a Nikon D40, not used it in years, same generation as the D90.
To capture the action, I would go for ...
Aperture Priority Mode
Shooting Mode: Continuous
AF Assist Light Off
AF Area Mode: Single
Try out the above settings today in different lighting conditions.
Take bursts of +/- half a dozen continuous clicks, wait a few seconds for them to be written to the card then do the same again.
On the day ....
be sure your battery's charged.
switch to Auto mode on the top dial, take a couple, then switch back to A mode. Auto might be good but it can bring the AF light on (battery draining & distracting), plus it can misfocus.