Good ideas, Mark. We have a set of offset spatulas of various sizes that get a lot of use. On the pastry bags, we use the disposable ones. I don't know if that's what the pros use or not. Either way, a comprehensive set of tips would make a nice gift.
Something else I just thought of (if a lot of cakes are being made) would be a cake turntable. From what I've seen, they're very helpful when it comes to cake decorating. There's an example of a plastic one sold here