What settings would i need in order to expose this sitatuation correctly?

I plan to take some friends pictures about an hour before sunset, they want to use these pics for their holiday cards. They want to be outside like I said an hour before sunset. My question is this, would I need to bring my external flash? I have a nikon sb600, with a nikon d80, I'm not too worried about taking dramatic shots or anything like that, just a family having fun for their holiday card. What settings should I use for the speedlight? I don't really know how to use it, I've been practicing, but I always end up messing it up afterwards. I was thinking of using a large fstop of 1.8 or 2, high shutter speed, and using the flash for fill light to lighten up any shadows, I practiced with ttl and manual mode, at ttl I think I have it at 14mm with the little diffuser pulled down at -3.0, and on the manual setting at 1/64, and to my untrained eye it looks like the TTL settings is easier to control with more pleasing effects, but again i have no idea how to use this thing and the manual sucks. I've also tried googling with little results. Can anyone help?

Here is a great resource for TTL and how to use it. I find it helpful and the instruction easy to understand. They cover topics ranging from fill flash to TTL and go quite in depth in the instruction.

https://fridayphotoschool.com/dl/