It sounds like you have a pretty good grasp on the situation, but ya your implied odds definitely improve with two callers because the odds of one of them having a pretty solid, but still second best hand to yours improve. I always take into account how passive/aggressive I think they are and what hand they're probably putting me on when calculating my implied odds, if I view them as a very good player that has a solid top pair or two pair hand that will make a strong bet on the turn if 3 to a flush doesn't hit and will be cautious if it does then obviously my implied odds are less than if they're a poor player with a top pair hand that will bet too little to make my draw unprofitable on the river and will likely call my raise. How many chips they have is another big one. There's definitely a lot of factors to consider with implied odds and how many people is for sure one them.
cheers,
Chad