Parental wedding speeches are the senior speeches in wedding protocols, and are allotted a bit more time than other speeches. That said, these speeches are supposed to be straightforward, not the notorious 'droning' speeches used as common descriptions of how not to give a wedding speech.
The average speed of a speech is 120 words per minute. A speech on an A4 page of about 300 words should take less than 3 minutes. Consider how much verbiage would go into a ten minute speech, and you can see why briefer is better.
Parents often do have a lot to say at wedding speeches, but after all, there's only so much of your feelings you can actually express adequately. Simpler is definitely better, and remember, you're supposed to be having fun!
The protocol for parental speeches varies, and both bride and groom's parents speak first. The order of speaking should be arranged in advance.
Paternal and maternal speeches may be conducted alternately, if so desired. If one of the parents doesn't want to make a speech, organize accordingly, but it's customary for at least one parent on both sides to speak.