I have a couple of questions that I would like help with
1. When checking in online on my mobile, will my boarding pass be available on my phone (I will be checking in for all of my family) - I will not have access to a printer.
2. Do I have to offer any other informtion online before we fly, the reason I ask is that in the UK we have to provide our passport details, but I cannot see anywhere to do that (I am traveling from Washingto to Buffalo)
You can check in beginning exactly 24 hours prior to flight time. Yes you can check in via phone.
Not sure if you can receive multiple boarding passes via phone. If not, you can always obtain boarding passes at airport kiosks. Your boarding position is based on when you check in, and not when you print your boarding pass.
No, you don't need to provide things like passport numbers or drivers license numbers.
Re: multiple boarding passes. We just did this today. My dad and I have the SW app so we had them on our phones, BUT we got four printed passes when we checked our luggage--one for everyone, irregardless of app or not. My dad had checked us all in, too. So, yes, if you have one person who is checking in everyone, then you will get boarding passes for everyone when you check the luggage, or you can print them at the SW ticket gate. I use the paper one for getting through security, but then use the boarding pass on my phone when I get to the gate.