Can I use Find My Friends for my family if we are using a single iCloud account?

Your family should not be sharing an Apple ID. Each family member should have their own Apple ID. Use Family Sharing instead:

Family Sharing - Apple Support

Set up Family Sharing - Apple Support

Family Sharing and Apple ID for your child - Apple Support

To answer you question specifically, for a single Apple ID, only one device at a time can transmit your location to your followers. So, you will not be able to track Family member sharing the Apple ID. See the section "Can I use Find My Friends on more than one device at a time?" in:

About Find My Friends - Apple Support

This is because to the outside world, you are are all one "person"

The Find My Friends feature relies heavily on an Apple ID (email address), which you are sharing.