In answer to the OP, I personally think its nice - kind of like a more specific Thank You card. I agree that the wording is a bit awkward but if it's a mass produced card, then it's bound to be, isn't it?
When I was first breastfeeding DD I used to get nervous in public, so every time I saw another mum breastfeeding her baby, it did make me more confident (I would think "If she can do it, then so can I" type of thing).
Many mothers are anxious about breastfeeding in public for various reasons. Anxiety affects your letdown, which probably leads some of these women to be physically unable to feed in public due to their discomfort, so anything that helps put these mothers at ease is a good thing.
Breastfeeding whenever, wherever needs is normal and natural, but unfortunately there is still a significant percentage of the population that is no aware/does not agree with this. The more confident women become breastfeeding in public, the less need there will be for "official" acknowledgement.