When you go into
MDE, click on Family and Friends and next to the person, click on Edit.
There you can set the permissions and under 'Invite to Plan and Share' you need to select This friend can 'View only our shared activities'. This will mean that they cannot see or change your FP+ reservations or ADRS.
Under 'Share Photopass Photos' you need to tick the box that says this friend can view and purchase my photopass photos.
ETA: Added a screenshot so you can see
https://flic.kr/p/nUp7Ub