We enjoyed Sevilla at the Casa Relator - it is nice to have a huge space in a place that is just a little off of the beaten path in old-town.
Location-wise it's very close to a huge square with 2 playgrounds (one for older and one for younger kids) that was fantastic for our kids. The street has everything you'd need within a couple minutes walk.
If you plan to hire / bring a car it will be a giant pain - keep this in mind if you're traveling with kids. Even loading and unloading was a nightmare due to the lack of places for loading / unloading near the house.
Otherwise, the space itself is utilitarian. The 'house' is 2 apartments on each floor put together with the same layout. You'll have most of what you need to cook basic meals (except an oven, which I suppose is still somewhat rare in Europe).
In terms of young kids - there's a central shaft running up through the house (that's made of tiles) so noise does carry between floors). The bottom (entry) floor is pretty much unusable space other than storage. If you have young kids you'll need to be careful as the stairs are steep - you can shut the doors to them, but toddlers can easily open these doors.
We stayed in the place with our aupair and managed well - as it has a living room that we were able to use as a playroom.
Overall - we are glad we stayed here.