In the mountains near Cernay and Thann, the lakes above Dolleren, Masevaux and Sewen (note the lakes on the map) are stunning, especially the Neuweiher. There's an auberge at the Neuweiher as well. Closer to Eguisheim and due West from there, almost as beautiful but with far more tourists, the chain of lakes running north from Col de la Schlucht are worth going to. I can recommend the Lac Vert (there's a good auberge here), Lac de Truites and Lac Noir to Lac Blanc (nice two hour walk). The route des Cretes runs along the cliff tops above all these lakes and also makes a very nice walk/s.

If you're into museums, the open air historic museum next to Ungersheim/Pulversheim 20kms south, the car museum at Mulhouse and the Musee d'Unterlinden at Colmar are all excellent. There are more if you're into this sort of stuff. As far as amusement parks go, I can recommend the Europa Park at Rust, just across the border and somewhat to the north in Germany. When I was there last it cost £12 per adult and £8 per child to get in. This includes unlimited rides and is really good.

Lovely excursions without getting into the car are: the round trip of the rue de Rempart (start at the house and 30 minutes later you'll be back from the other direction); the walk up to the Trois chateau (you can see these from the village) is a lovely and stiff 2 hour walk all uphill. If you're not into stiff walks, then I recommend parking at Husseren (the next village up) and walking from there. If you're really opposed to physical activity altogether, then there's also a parking lot right near the Trois Chateau themselves; The parc de Cigognes (storks) at Eguisheim, ten minutes stroll from the house is also nice.