I would say make the bet for the first series ONLY now.
Then, if they win, roll as much as you want into next series. And so on...
I say this for two reasons...
This way you are in control of your money and can pull back some between any series.
And.. They will be a DECIDED underdog every series. This method will pay you far more than 100 to 1 if you roll everything over.
Of course, the most important reason this is good is because they have a snowball's chance in hell of winning all these series back to back as large underdogs. If you can just get the first two, under my plan, you will be a HUGE winner.
If I do say so myself, this is a BRILLIANT plan!