I've never done Saturday only, we normally do all three days. So not sure how it goes but last year the grandstand access on Friday and Saturday was on a roving ticket, so you could get into any grandstand as long as you had a grandstand ticket. But last year I have never seen it so busy on Friday/Saturday and would expect the same this year. So your DH could get roving grandstand or they could just let hime into Copse.
For you, assuming he's in Copse I would aim to sit at Becketts, it's a great high speed corner and has good view for general admission and you won't be too far away from DH. There is also GA banking from that corner up to Copse but none going the other way towards the pits really. I sat at Becketts in '99 and it was great. You've also got a TV screen opposite you on the inside of the circuit.
I've never been in GA on a Saturday so no idea what time you need to get there but it shouldn't be too bad I would think/hope.
Looking at last years programme, the Saturday timetable was:
10 - 11 F1 free practice
11.25 - 12.10 Porsche supercup qually
12.30 - 12.42 Blue Eagles flying display (helicopter equivalent of red arrows but not as exciting)
1 - 2 F1 qually
3 - 4 GP2 race 1
4.45 - 5.15 Historic sports car challenge race one
In addition to all that they now have lots of activities around the circuit, music, competitions
Car parking is fine now, expect a bit of a queue to get in but not the hours and hours it used to be.
I'm quite jealous, we're not going this year as was hoping to be heavily pregnant and by the time we realised we wouldn't be the tickets we wanted had sold out.
What teams/drivers does your DH like? Some of the teams have driver appearances on the Friday and Saturday, all the team stands and merchandise are behind the pits straight, its worth having a wander first thing and asking/checking out the boards for driver appearances to see if you get to see anyone, but it will be mobbed! Coulthard did one last year and you couldn't move.
What to take, well it depends on the weather, I've been freezing and sunburnt over the years, so it may be sunscreen or it may be a brolly. Take a folding chair if you have one. Take food if you don't like overpriced greasy burgers/pizza's/chicken. Take a portable FM radio each with in ear headphones if you have them and tune into Radio Silverstone for commentary, interviews etc. And nothing can prepare you for just how LOUD it is.
Have fun!