You cannot buy a 2 month pass, you can buy one month, then another month, then a week, then if you have 4 or 5 days left, just go prepaid, the daily limit is capped at the price of a daily oyster travelcard.

Tuffnell Park I chose at random, it is proper London and I am sure you will have a great time, Kentish Town next door is positively gentrified, it even has an organic shop!