Little Miss Sunshine is a great text. Sure, it was on the suggested related texts list, but it's there for a reason. You can get a lot from it. I actually sat down and took a few notes on it when I was considering it as one of my related texts.
It is definitely a good text choice.
It is a great movie, and a great text to use for belonging (family etc). The only problem is that IMO it seems to be a little bit overused, and if it's overused it is a lot harder to stand out when discussing the thematic concerns, values, concepts etc, because pretty much everyone who does this text, will write about these similar aspects of belonging.
This is all just speculation however, so if you're confident enough that you can analyse this text well, then by all means go for it!
If you are able to develop complex ideas about it then go for it, the fact that lots of other people do it allows you a chance to differentiate yourself with superior ideas. I say go for it, but make sure you do it well, think outside the square and get things out of it that others may not be able to.