Sounds great to me. Generally bilingualism doesn't hurt children and can sometimes even lead to better performance in school or cognitive advantages (there's some current research in this). But there are two things to watch out for:

1. That's so many languages that they might not learn all of them to any useful amount. Many children experience attrition where they can use a language as children and then later, as adults, forget it. With 5+ languages, that's very likely in this case. So decide which languages are important. For example, I know that a lot of Arabic-speaking families in the United States have children who do not retain their ability to use Arabic as adults if only their parents speak it-- they know a little, but not very much. German, of course, will come naturally through schooling there. And probably English. The others you'll have to decide about. There's certainly nothing wrong with singing to your child in French, for example, but there's no chance they will actually learn French from that alone, or remember it well later. But it might HELP if they do study it later in school or want to learn. So this exposure and experience only matters if they actually use the language later. No harm in exposing them to a lot, but make sure to focus some on the ones that matter most to you or might matter to them.

2. One problem that can happen is that young children can get confused about separating the languages they know. So this can make them a little slower in school at first or a little confused socially, when they first leave the house and then need to speak one language with one person, and another in another context, and so forth. But this corrects itself naturally. With so many languages, this could be especially confusing at first. But having different contexts at home (mother and father having different languages, for example, and relatives, etc.) might help.

Also see the discussion here:
http://linguistforum.com/language-acquisition/teaching-a-foreign-language-to-a-baby/

3. Specifically in this case with so many languages you might want to do some research on polyglot children (a polyglot is someone who speaks many languages). This is beyond bilingualism, trilingualism, even normal "multilingualism". I'm not saying that's a bad thing, but I think it's fairly rare. The simple answer might be that it doesn't usually work because the children end up limiting the languages they actively use to a few (around 3?), regardless of input, but I don't really know. Children will absolutely learn to speak and communicate well (might take a little time to adjust to some things) but that doesn't mean they'll learn ALL of the languages around them, just those that are important, whatever that means to them.

Also see