You might know of these already, but two quick Barra recommendations (GlasgowDave and I were there at the beginning of May)
Kismul Cafe - the Indian(/Italian) restaurant in Castlebay. Pop in and book, it gets quite busy and it is not very big, but the food is great.
Barra airport has a cafe - there is no obvious sign, we stopped because we saw lots of bikes outside and sure enough there were lots of cyclists tucking into soup and cake in the one big room which is cafe/arrivals/departures/security.
Have a great great trip,
PerkyGirl
(we are off back down to Moffat this weekend, will be more tandem and less car this time!)