You’re right. That itinerary is pretty ambitious. But it’s doable.
I don’t know of anyone who could organize a trip of this scope. Most relocation tours focus on one region. I would suggest planning the itinerary yourself, contacting real estate agents and schools in the areas you hope to visit in advance so you can have meetings and appointments lined up. I would also recommend renting a car to get around. With this timeframe it’s best to have that mobility.
As far as international schools, there is one on the Central Pacific called Falcon International: http://www.falconicr.com
And on the northern Pacific, near Playa Flamingo, you’ll find Country Day School – Guanacaste ( http://www.cdsgte.com) and La Paz (www.lapazschool.org ), as well as Green Life Academy in Playas del Coco (http://greenlifeacademy.wordpress.com). There’s no major international school in the Southern Zone. But you will find a smaller school that is well-regarded called Escuela Verde: http://www.escuelaverdecostaballena.com