Going back about 12 years but when my late Mum started to find it difficult I was able to get a drop off ticket. We sat in the lower Trinity and I was able to drive into the North Stand Car Park stop for a few minutes at the disabled entrance, take her in and sit her down before I drove out to park up and then rejoin her.
There was no charge for this and I don't think there was any limits on arrival time, although we obviously arrived more than just 20 minutes before so that I could get out going against the traffic to park up and be in for kick off.
It might be worth you contacting the club if this is an option for you.