Affordable Accomodation in Fukuoka

Family of 5 with budget less than JPY 12K per night travelling in Dec...we ok with apartments but Airbnb has very limited choices for our family size.
Thank you!

For a family of 5, in the same room? That is nearly impossible for a typical hotel - unless perhaps one of you is a young child who could share a bed. You could look at a guesthouse like Khaosan which has both a triple and a double, at a price close to what you are asking. See:
http://www.khaosan-fukuoka.com
Another possibility is staying in a Japanese inn (ryokan) if the place will accommodate you with an extra futon or 2.
See:
http://yokanavi.com/eg/landmark/keyword/154
You'll have to ask each place though.
There is a lot to see and do though, have a look at:
http://www.thejapanfaq.com/fukpic.html

and for some video previews of where you can go, try:
https://www.youtube.com/playlist?list=PL7LcPcmoSg-j4RLa6iC7ayvBAbOn8-0...

Also you'll find it quite a bit cooler than Singapore in December, so bring enough warm clothes with you.

Hi Ken, thank you very much for all the links, indeed very useful!

Just to add, we are 3 adults + 2 kids (10 and 6 YO) so will be able to fit into quad room