There's really no substitute for getting the mic as close to the person's mouth as possible, as that's the only way to capture their voices separately from the surroundings.
A $20 mic at close range will sound better than a $1000 mic twice as far away.
If your recording options are limited, go with cardiod mics placed as close to the talent as possible. Shotgun mics are not recommended for indoors because they tend to adversely colour the timbre of the sound.
Hope that helps. In your case, booming is preferable, or perhaps omni lapel mics attached to wireless receivers or portable minidisc might be the best solution.