Txaro is the most welcoming host you could wish for. We are a family with one small child and it was perfect. I worried that we were a little far out from the centre of town, but Bilbao is so small and all of the transport links are less than 5 minutes walk away, so the location is perfect unless you want to be right in the hustle and bustle, which we didn't.
The apartment is spotless and Txaro has thought about pretty much everything you could need, including toys for my daughter and super useful things like a baby bath. Her communication and help also make a big difference. Highly recommend.