My wife has ADHD and I have autism. I do the planning, she does the going with the flow forgetting and then re-remembering/getting reminded who she is seeing.
She has been to 2 Glastonbury's and loves it, but does take some time out of the main entertainment areas to do some craft etc to help focus her mind and may just wander up there on her own while the rest of our group are watching an act.
She lives her life with reminders/alarms on her phone to help her remind her of what she wants/needs to do. She finds doing that helpful not just in the real world but at Glastonbury too.