Iona,
To answer the question
"Where is the best place to stay?" is like answering
"Which child is your favorite?". Too many choices that I love for different reasons!
But I have an answer for you, I promise. With a 10-year old boy, and your comments about fast rides, I am thinking that you are going to be spending more time at Hollywood Studios, and probably also Epcot, than I do with two little girls who are all about princesses and castles. I would recommend the
Beach Club or the
Yacht Club. First, the pool is a great option for him, with a pretty great slide that is still to "big kid" for my younger ones. But for him it will be fun.
You are also a quick boat ride away from Hollywood Studios, with the Rock 'n' Roller Coaster, Star Tours, and the Tower of Terror. By your visit in March you will also be a quick walk away from the newly opened Test Track, as well as Soarin (maybe not fast, but still a great ride!), and Mission: SPACE.
As for La Nouba, great choice! Some good places for dinner before hand would be to go to Bongo's (Cuban), Paradiso 37 (Latin and Central American) or Raglan Road (Irish). There are several other choices, and your 'boys' may like a visit to Splitsville for some bowling and other fun.
Write me back and we can work on your next part of your planning, if needed. Maybe we can chat about the Child Activity Centers that could free you and your husband up for a date night out?
Have a magical vacation!