I've been going to the Lakes for years as I have family there. I think at 10 and 7 the kids would love it- swimming in a lake is so much more refreshing than the sea as no saltwater, great for kids wanting to be constantly in the water! My advice would be if you can find a lake resort with a 'beach' (usually man made) then it won't be too different. The only tricky thing about being by a lake is if you don't have a beach or sloped area (we tend to hang out by the jettees) then you're restricted to jumping in and climbing out, sometimes over rocks. We found it tricky last year but mostly because we were with toddlers and the village where my family live doesn't have a beach. We drove out to a beach further round the lake and this was much better as we had sunbeds, soft sand and a gentle slope into the water. It was quite expensive though if you were going to go there every day I think we paid around 20 euros for the day.
Hope this helps!
