Hello Samantha,
about the Airport:
That would be HAJ, the local Hannover City Airport, about 40km away from the Playing Grounds.
Airtrip via any Airport to a major EU Airport like Amsterdam, London, Paris or Frankfurt, Germany. From there the Airtaxi to HAJ (Hanover Airport). Your local booking office can give you better details if you ask for a connection to HAJ.
According to Taxi Calculators, the Fare would be around 50-60 EUR (1.40 EUR per Kilometer) for a single trip. If you get a 7 Person Taxi Bus, this would be low cost for you - split by 4-5 persons...
Or: Airport Langenhagen by train to Hanover Central Station, switch train to Nienburg City Station, from there by bus to Brokeloh Village. But this will not work not on Sundays.... neither to or fro.
Anyway, this is the Google maps link from HAJ to Brokeloh:
About a possible Hotel... there is one about 500 m from the Playgrounds. Its the "Dreschhof".
http://www.dreschhof.de/ Nice, clean, prices reasonable, they have much intl. guests (yes they can speak english/french). But chance maybe that it is already booked out for next August. Just try and give them a call.
And - i don't know if they are coming this year too, but there would be the socalled "Viking Hotel"... they rent out viking tents.