Edge Class - Assigned Dining Time

[Sandy1975]

We are going on the Apex in November with my MIL. We have anytime dining and she has 6PM sitting. My husband wants to move to 6PM sitting but I think it is better if she changes from early dining to select. I have 2 questions: 1)If we move to early time dining and link our reservations,  do we get a restaurant assigned and we go to that restaurant every day or can we rotate amongst the 4? 2) There is no select dining available,  can we switch her when we get onboard? I was thinking I could ask the Host when we have our concierge lunch on embarkation date. Or is this not possible?

Thanks