Based on the description you gave of the pond these trout will be going in, I do not think any species of trout will hold over through the summer months. This means the stocking of trout will be a seasonal thing.

Rainbow trout are usually the species most commonly recommended for ponds. They tend to be easier to catch and less piscavorous than brown trout. Brook trout are the least tolerant of warm water conditions than either of the other trout. I am a big fan of brown trout though as I like their aggressive nature towards minnow imitating baits. Rainbows are the jumpers of the trout world though and that makes them fun to catch. I like to stock a combination of rainbow and brown trout. We usually stock 100 trout each spring, usually a 60/40 split between rainbows and browns. However next year we are thinking about putting 10 brookies in and lopping off 10 of the rainbows.

Realize that if you release the brown trout, they are nasty smart and may never be hooked again leading to them dying before you can catch them out before the warm temps set in. The rainbows seem to be easier to catch multiple times. These are just all my personal experiences though and I am sure others may have other experiences and or advice to give.