Is your difficulty in helping them book space due to lack of award availability on their preferred dates?

In a transaction like this, it is all about finding award space.

Might be prudent to "de-link" the tickets and the stay at your house in Mexico: Suggest they use the miles for any flights of their choice for them or their friends anytime in the next year to any destination where the miles are sufficient. They can then buy the tickets to Mexico, preferably using a companion ticket acquired through the AS visa card if there are two of them.

OR, perhaps there are seats to one of AS many destinations in Mexico, and they could then get to the airport nearest your house on separate tickets.

If they are the "slow and spotty" type, beware of them wanting to change the dates of award tickets after you book them and there being no space available on the new dates. Best to let them know, and get them to acknowledge via email exchange before you ticket that date changes may be difficult.

The above strategy is not pretty, but it gets the job done and wraps this matter up for you.