So reading between the lines, the owners aren't as interested/invested in the place now that their grand kids no longer ride? And that they're doing the minimum to keep the place going, not actively involved?
If so, then I think you have to be very careful and tactful about how you approach this, because if you're perceived as difficult, complaining or high maintenence, they may decide that having boarders just isn't worth the trouble.
So definitely approach it with an attitude of what YOU can contribute to make these things happen while not causing them too much inconvenience.
In re: the poster who asked about fixing things around the barn, I think what you did sounds lovely and you're probably a prize boarder. However, there is a line you shouldn't cross w/o asking permission from the BO first; and that line is defined by actually altering the BO's property or doing something that involves heavy equipment or a lot of power tools.