I would ask the former activities coordinator (or whatever she's called) to maybe address the group with a small speech saying she's retiring from her position, and everyone should welcome you as the new coordinator, and be as helpful as they can be because not only are you new to the position, you're new to the group, etc.
If you do get anyone who expresses anything other than enthusiasm for what you're doing, then sweetly say something along the lines of "I'm really sorry you were disappointed, I'm new and I'm trying my best, perhaps you could help me with the next program and show me how to do it better?" Suck them in to helping you. Ha!