You will need a fan ID each which is easy as you just need to ring up with your details to get them.
I'd also add that you should link your and your son's Fan IDs once they're created, so you can select and buy your seats together in a single transaction.
When I was over for the Leeds game last season I was in the Lower Holte and we were standing for the entire 90 mins. Not an issue, and indeed preferable for me, but would be problematic with an 11 year old. I'd suggest going for somewhere where standing is less of an issue and seeking advice from the regular attendees on here as to where's best.
When I take my nephew we go in the upper tier of The Doug Ellis, towards The Holte End (P1) It’s great for picking up the atmosphere of The Holte whilst still being able to see, and not having such direct exposure to ‘language’.
There is a bit of a restricted view thing going on towards the front because of the rails at the front of the upper tier, but you soon get used to kind of ‘seeing round’ them & there’s usually decent availability there.
It’s impossible to get food or drink or get to the toilet at the times you’d like to, but we amuse ourselves with a walk to the top of the stand and a wander down to the other end to wave at the away fans!