does this tip the balance?

[Yora]

I don't think they make much of a difference. You allready have a party of 6 and the dire badgers only have 28 hp, AC 16, and deal 1d4+2 damage.
Even if you use them as cannon fodder to occupy the dragon, I think he'll chew through them in 2 or 3 rounds.
If the PCs can't take the dragon on their own, the badgers won't make the difference.

If you don't want the players to be defeated, make the dragon a size smaller.

But I'm actually not so sure it will kill them. The +23 to attack and AC 23 is a bit tough and 8d8 breath weapon is not just a little sting, but thankfully a blue dragon has only a line attack with his breath, so if they spread out he can only hit one of them with his breath instead of half the party. And if they know they are going against a blue dragon, they should try a way to get some lightning protection for their most threatening looking warriors.