Swift Aid grants a lesser bonus than the normal aid another action
The bonus granted by the feat Swift Aid is correct: the feat's benefit does, in fact, only grant "your ally either a +1 bonus on his next attack roll or a +1 bonus to his AC" instead of the normal +2 bonus granted by the aid another action.
Ask the GM if your own aid another actions stack
The GM must determine if the same creature can use aid another on an ally multiple times and in the same area (like the ally's AC or attack roll). The text of aid another only says, "Multiple characters can aid the same friend, and similar bonuses stack," and is silent on whether one character can aid the same friend multiple times. You'll have to ask the GM how this works. I'm certain a creature with the feat Swift Aid can, in one turn, aid two different allies, but it's up to the GM whether the creature can aid the same ally twice in different areas or if the ally can aid the same ally twice in the same area.
This GM would likely allow a PC that wanted to spend actions aiding another to do so if that's how the player wanted to have fun, but this GM would also likely nix recruiting a band of halfling investigators that've all taken the investigator talent effortless aid and the trait Helpful.
The answer should be Yes, but politeness demands asking the GM anyway if aid allies can be combined with Swift Aid
The cavalier order Order of the Dragon extraordinary ability aid allies says
At 2nd level, whenever an order of the dragon cavalier uses the aid another action to assist one of his allies, the ally receives a +3 bonus to his armor class, attack roll, saving throw, or skill check. At 8th level, and every six levels thereafter, this bonus increases by an additional +1.
Because the special ability aid allies doesn't care how the cavalier is aiding another, its benefit should replace the normal benefit of the feat Swift Aid. However, once again, as it's potentially abusive to recruit a platoon of helpful halfling cavalier/investigators to follow around a PC, the GM should be warned ahead of time about this interaction.