2 Blue LEDS , in series or parallel/ optimal power resistor type of batteries compact area
If you wire your LEDs in series, as you say they have a Vf on 3.2 then there is no chance of powering them with 3 AA batteries. You also need to remember that whilst AA batteries do say 1.5V this is a fully charged battery. AA batteries whilst discharging do lose some voltage (I've had AA batteries at 1.35V and they still powered my wireless mouse). Rechargable AA batteries start at 1.2V if they're NiMH's.

You could try using 4 rechargeable AA batteries connected in series, giving you 4.8V supply. You would have to connect the LEDs in parallel however, otherwise the Vf is going to be more than the batteries can supply. For mid-luminosity you probably want around 15-20mA, with 4 batteries and 3.2Vf LEDs then 82 ohms would be fine.

Bottom line, 4 rechargeable AA's connected in series, 2 LEDs in parallel, 82 ohm resistor connected to each LED