You could drive to SS but, yes it would be a long haul and bear in mind July will be hot no matter where you are. Stick to the coast there is lots to see. Monsarrat is a nice day trip. SS would be very crowded but oh my I would like to say try it. Don't know how old your junior travellers are so that must be considered. Caution!!! Don't try to do too much!! 2 weeks is only a little bit of time to really experience any part of Spain. Sun Screen, hats and have a good time.

Please note Girona is hilly.

Thanks for the advice. I totally agree that adding San Sebastian is dicey because of the long drive. We have done 5 h drives before between different locations in other countries but I'm wondering if 7 h is just too much. I also agree it is not great to try to do too much but I'm not sure when we will make it back to Spain so I don't want to do too little either.

Could you please elaborate on Girona being hilly?
Do you mean it is a difficult place to drive or tiring to walk around with the kids? I think I did not understand your point.

Girona could be hard to negotiate with children. I did not have a car in Girona, but in most older Spanish towns and cities a car can be more of a burden with reagrd to parking and the narrow streets.

San Sebastian/Donostia is too far to drive.

What you could do is stay in Barcelona, fly up to San Senastian stay there a few days, where there is a beautiful beach and then rent a car to visit the many worthwhile nearby towns.

Many Madrilenos go there and northern beaches during the summer.

I was hoping you would not say SS is too far to drive. However, it is nice to get honest advice. We have done 5h drives before in Greece and Portugal but maybe 7h will push us over the edge.
I had not considered flying. Is it cheap to fly from Barcelona to SS and what airlines should I look at? Thanks!

for flight alternatives you may check www.skyscanner.com

I've been to Barcelona in late Sept when the temp was in the high 20's with humidity and had difficultly site seeing during the day. Personally I don't care for their beaches and would spend the time here only to visit the major sites. If beach time is essential perhaps Valencia is a better option and would offer more for families. I highly recommend SS and the Basque country. You can fly from BCN to SS on vueling airlines. Cost is inexpensive. An itinerary could be US to BCN then fly directly to SS/Bilbao (depending on you arrival time) - make SS your base to explore the area - fly back to BCN ending your trip here.

Thanks so much for your helpful advice. I will look into flying to SS and spending the majority of our time around there.
Less time in Barcelona and Costa Brava.

Girona is not really hilly - not the roads we used anyway. We stayed in an area near the city park and there was plenty of parking on the street. Getting in the first time, that was a pain (because we did not know where we were going) but after that it was fine. Walking up and around in the old quarter, that is fairly hilly. We found it a really good base and there are a lot of summer activities in the city park.

The old town of Girona, where the sights are located, is very hilly. I think it's actually worse or at least on par with Toledo. Outside of the old town by the riverfront it's not. But if you want to stay in the old town be ready for steep hills.

We didn't stay in the old town - I definitely would not drive up there. We did walk to the old town from our apartment and I don't remember it being all that strenuous.. but remembering and reality are two different things.

About the fabulous Basque Country: http://tourism.euskadi.net/en/

All about going for pintxos in food crazy San Sebastián (Donostia in Basque): http://www.todopintxos.com/home/home.php?lang=en

Plenty of day trips opportunities around San Sebastián. I recommend to have lunch some day in either pictoresque San Juan/Donibane just some 3-4 miles east of San Sebastián or in tiny Getaria just west of town.

Several great seafront restaurants with lunch bargains in San Juan/Donibane. The bus leaves from Plaza de Guipúzcoa in Central San Sebastián about once an hour and takes some 30 mins. Also possible to walk here along the stunning coastline in some two-three hours (including a 2 min boat ride, the boat leaves all the time):
http://www.euroresidentes.com/euroresiuk/Spanish_villages/san-juan.htm

Fabulous seafood restaurants in Getaria, something like this (Elkano is the most famous, but there are more excellent small restaurants down in the tiny harbour): http://www.thepauperedchef.com/2007/12/elkano-in-getar.html

Go some miles inland to Tolosa for visiting a different kind of Basque town, the best steaks in the world and the delicious Alubias de Tolosa (Bean dish ala Tolosa)
http://www.tripadvisor.co.uk/Restaurant_Review-g1064362-d1074845-Reviews-Casa_Julian-Tolosa_Guipuzcoa_Province_Basque_Country.html#REVIEWS

Wow, thank you all, this is great information.
I am in the process of figuring out lodging at the moment (rental villas since we are a big group). I just ordered Rosetta Stone so the whole family can learn some Spanish before the trip.

It appears that we will be in SS during the 'Running of the bulls' festival in Pamplona. Would you folks recommend checking it out? I think it is about 2h away from SS. The group can split up if you think it is not a good festival for kids.

The San Fermín-festival in Pamplona is a fabulous party and something very special. Even if it's far from a kids festival there are lots of kids and families up here. All kinds of activities for kids around town all the time, a fun fair etc.

Fun fair: http://www.sanfermines.net/ingles/barracas.php
Children's events: http://www.sanfermines.net/ingles/con_ninos.php

That sounds really fun. We will add Pamplona to our list.
We have decided to stick with our original itinerary: 15 days covering Barcelona (3 days), Costa Brava (5 days) and San Sebastian (7 days) and driving between the places. It is a lot of driving but I think we will be ok.

If you think Girona to SS is too long for a direct drive with the children, you could spend a night somewhere in between, e.g., Zaragoza or Toulouse depending on the route that you take.

I think the kids will be ok with the long drive.
However we would love a couple of nice stops along the way.
Are Zaragoza and Toulouse nice for lunch and walking around?

Is the drive really boring as it is all highway or is it scenic as well?

Sorry, I haven't been to either one yet. Going to NW Spain this year and NE Spain next year. So, they'll be on next year's itinerary.

Both are cities but look to have some very interesting sites. And, both will have a carousel that your kids might enjoy a spin on.

Google images of both to see if you like the looks of either.