I'd go with even larger trout than A.P suggested. At least down here, 12-14 inch trout are relatively cheap -- about $2-$3 each. I can only keep trout from October through May, but even in that short period of time, they usually grow a few inches on pellets. I stock a mix of rainbow and golden trout. The golden trout are mutated rainbows, and are just fun to have in the pond since they are so easy to see, especially at feeding time.
If available, brook trout are just plain fun to have, they are incredibly beautiful, and they are as easy to catch. Brown trout are a lot harder to catch, so they aren't quite as popular.
Trout probably will not reproduce in your pond. If they will live through the summer, just plan on adding some each September or October.
