Explore the abbey in the morning - take a picnic and have lunch on the banks of the lake next to the ruins of the Abbaye du Repose. Then afterwards go on to Lac de Guerledan where you can relax on the sandy banks, swim in the lake or the children can play in the playfround. There's a restaurant where you can (obviously) either eat or just sit down on the balcony for a drink or ice-cream.
A thoroughly relaxed and gentle day out.
Unfortunately I don't know the history of this abbey and have never got around to finding it out