I did BRU for the convenience of our friends and family, and it was less expensive than BBB.
I used the Amazon registry for my own conveneince and as it turned out half the gifts were from amazon...so it worked well for the gift givers too!
Amazon also has a universal registry that allows you to add items from any other website. It works reasonably well, however I couldn't add something from Pottery Barn because of the way PB's webpage was set up. You might be able to add the Land of Nod items there. Then you could register at BBB as well.
Amazon registry was awesome. BRU is just a crappy place to shop. BBB staff are very helpful but I get the sense they are just telling me what I want to hear to make the sale rather than offering informed, unbiased advice. But I could be wrong...
You might want to stick to two registries. I personally hate when 3 places are included. And it is just more for you to keep track of.