Yuzawa to Akita to Sendai loop drive?

I'm planning a 7 day road trip with my mum and 3 kids, setting off from ishiuchi, near Echigoyuzawa and driving north to Akita for their lantern festival in August.
I would like a recommendation about how to best break up that long drive north: stay overnight somewhere in Tsuruoka or Sakata? Ideas for any interesting stops along that coastal route? Driving from Akita to Sendai - recommended pit stop (kids have approx 2 hour car limit). Should/could we go to Geibikei? Then on to Sendai.
After the Tanabata festival we need to go back home to Ishiuchi. Any advice about a good place to stay, something to see/do on the way? Initial thoughts are to stay somewhere near Inawashiro - again to break up the journey and see a new part of the country.
I'm particularly interested in kid friendly sites and visiting great onsen. Appreciate any ideas. So far I have booked accommodation in Akita and Sendai.

1)
How about Yunohama/湯野浜 or Atsumi/あつみ Onsen
http://yamagatakanko.com/onsen/
or camp site?
http://www.walkerplus.com/spot_list/ar0206/sg0112/
http://www.jalan.net/kankou/060000/g2_04/

for kids :
http://yamagatakanko.com/spotdetail/?data_id=2601&yc=spot&ya=23&yp=1
http://yamagatakanko.com/spotdetail/?data_id=4293&yc=spot&ya=23&yp=1
http://www.tsuruokakanko.com/cate/p0188.html
http://www.city.sakata.lg.jp/ou/norin/norinsuisan/suisan/3003.html
(Tobishima/飛島 is small island by small ferry travel 75min far)
http://sakata-kankou.com/spot/161

2)3)
might answered when remembered.
http://en.tohokukanko.jp/spot/
http://odekake-k.com/

This is for kids as (?)th stop around Sendai from North very famous all.
http://www.tohoku-safaripark.co.jp/
http://www.kankaku.org/
http://www.uminomori.jp/umino/
http://www.city.sendai.jp/kensetsu/yagiyama/
http://www.benyland.com/
http://zao-fox-village.com/

Besides Tsuruoka (for Dewa Sanzan) and Sakata, Niigata is also worth a visit. A boat ride on Mogami-gawa would also be nice.

Before driving down to Sendai consider visiting beautiful Tazawa-ko and nearby Nyuto Onsen.

Gembikei Gorge and Geibikei Gorge are good scenic sites whereas nearby Hiraizumi is also worth going.

Popular side trips from Sendai are Yamadera and Matsushima.

After Sendai Kitakata is worth a stop for its ramen and Aizu-Wakamatsu for its castle and samurai history.

Besides Nyuto Onsen other onsen destinations worth considering include Hanamaki Onsen, Naruko Onsen, Ginzan Onsen, Zao Onsen and Akiu Onsen.

For “kid friendly sites” consider the Kankaku Museum, Anpanman Children’s Museum & Mall and the Zao Kitsune Mura.

The Dewa Sanzan are pretty amazing. How well they can handle something like Gas-san would depend on ages and their hiking experience. Haguro-san has a road to the top though and lots of parking so it's a really easy trip.

If you like the movie Okuribito, at one point Sakata had a ton of sights from the movie open to the public. The most interesting was the house presenting the office where lots of props were on display.

I loved Zao onsen.

I guess a lot depends on your children's ages and interests.

Thank you for the replies. I will try and get accommodation in the kitashiobara area and check out some lakes with the kids on the way back to Niigata from Sendai. Found a couple of pre-2011 guidebooks which have slightly more information about the Tohoku region. Struggling to find a budget halfway stop off point between Niigata and Akita - any suggestions?