I'd suggest looking into RCCL's Voyager, it cruises the Western CAribbean and I understand sometime this year it will be alternating with Explorer of the Seas between the east/west. They are wonderful ships for cruising with the family and the kids program is also top notch, your 10 year old should have a lot of fun.
You may also want to try posting someting simular to this post in the "bargain finder" and see if any travel agents can come up with something to suit your needs.
Good luck and Happy Cruising
Tuesday Chat Host