I can say with 100% certainty that it doesn't matter what order the Sims 3 expansions are installed in. I had the base game, and Ambitions installed before I got WA or any Stuff Packs, and I also installed Late Night before Fast Lane Stuff. But before I did any of that, I contacted EA customer support and they confirmed that it doesn't matter what order they're installed in, so long as you use the most current expansion installed to run the game. So even though Late Night will be the last expansion you install, you'll still use Outdoor Living to run the game.
For Sims 1 and 2, it definitely mattered which order you installed them in, but for Sims 3, it doesn't.