Not really funny enough for a comedy; far too silly for a drama... The kids are likable, David Tennant's as highly watchable as always, there are a fair few mildly amusing moments and it's entertaining enough. But, you rather get the impression that none of the film-makers really had much of an idea about what they were making or who they were making it for.
Clearly a dramedy.
http://tvtropes.org/pmwiki/pmwiki.php/Main/Dramedy
Film is an art form and good art always tries to break through established categories to invent things which are new and refreshing. Has been going on for thousands of years. We no longer paint like the Ancient Egyptians, for example.
I think it's always a mistake to set in stone the allegedly defining characteristics of genres of anything! Why not sit back and see what unfolds? Works for me, and I don't get hung up about what a comedy should be or what a drama must contain etc. Life is a glorious mix of loads of stuff, if we're lucky. Just as this film family demonstrates.
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