First of all, congratulations on your pregnancy! I was never really on board with the whole registry concept, but I was told by MANY people that I had to do it for our baby shower. I decided to register for a small number of things - some big ticket items for people who wanted to group together and buy something nice and useful and some small ticket items to cover the range of gift budgets. There were still plenty of people who purchased things that weren't on the registry, so don't worry at all about that - people will do what they want to do, but the registry can help them to at least see your nursery/color choices. One word of caution - a friend who included everything under the sun on her registry ended up getting lots of the "nice to have" stuff and didn't get some of the "need to have" stuff, so try to keep it small. You can always add things later, as many people will want to give gifts after the baby arrives (a reason to check your registries often to make sure things are removed once they're purchase) Make sure that whoever throws a shower knows that you want to downplay the registry part of the invitation (but I don't recommend excluding it altogether, because some people really rely on it), as there are many tasteful ways to mention it without making it seem like the shower is all about gifts... which they often are ;)
As for BrUs, I'm with you. I absolutely hate that chain, but they know they're the only game in town and that people tend to overspend for babies :0 I suggest that you leave a few things on the BrUs registry but move most to Target (I wish I had). Ask both of them about their policy for returning items that don't have a receipt, as you will certainly have this situation. Then, RELAX and enjoy all the preparations for your little one...