From my experience, mixing those two tangs with a foxface is a bad idea unless the tank is 300 gallons or more. Sailfins are a lot more aggressive than people give them credit for, and yellow tangs have a tendency to be aggressive also. With a fish that's the same basic coloration this can be worse. Mixing the two dwarf angels is risky in a tnak that size, also. You can try it, but I would recommend adding them at the same time. This was neither has established territory to defend.
As to what you can add without the skimmer, so long as you're keeping up with water changes like you plan on, it shouldn't be an issue at all.