It certainly looks a busy schedule to me but I´m probably saying that as a non driver . I´ve been to País Vasco 3 times .. always with friends driving from Madrid . We always leave one day free to relax BUT we do get to see a lot .
Other places you should consider visiting is Donostia-San Sebastián .. I would love to live there one day ! And the spectacular island monastery of San Juan de Gaztelugatxe . The monastery itself is a tiny brick building .. nothing special ..but to go there you have to walk up many steps over the sea and up to the top of the rock . Absolutely stunning !
I´ve never been to Guernica .. but if you´re interested in history then it would be a good choice .. I´m embarrased that I haven´t been there !
In Bilbao : I like modern art upto a point but found the art in the Guggenheim a bit too contemporary ! However the building is magnificent .. really takes your breath away . Inside is a café and a restaurant ... The restaurant is considered one of the best in Spain . It cost me €120 just for one person ! The food and wine and service were all excellent .
The Estación de Abando is worth a quick visit for it´s amazing stained glass window depicting Basque life . Nearby is the wonderful Café Iruña .. great for breakfast .. but also open for lunch and dinner . A real classic !
Finally please try and go to Portugalete .. a suburb of Bilbao ( you can go by metro ) and take a ride on the truly amazing Puente Vizcaya
www.puente-colgante.com across the water . This area , as well as Getxo is a wealthy area of Bilbao .. There are some great places to eat Pintxos outside or just take a walk by the water .Last time I went with a Basque friend and we went to Portugalete in the evening ... Very beautiful ! I would say that was my most perfect moment in País Vasco . Just walking by the water , drinking Basque white wine and eating wonderful Pintxos on a hot evening !