Couple of misconceptions here. Using pine needles/duff does NOT drive pH down. I've tried to adjust my soil pH down using pine needles, it doesn't work. Pine bark on the other hand, when mixed in at very high ratios, does drive pH down (pine bark has a pH of 4-4.5), but you have to mix it at least 25% to see a pH change, especially if you have high alkalinity (which I do).
Pine does not stunt plants. Container growers on the east coast use pine sawdust as media all the time. I use pine bark as a component in my potting mixes. It DOES rob N, so they inject more to compensate. You're talking about using logs, though, I assume. In that case, no change in Ph will occur, except at the soil-wood interface, which is minimal for a log. Mixing in chipped wood would give you more pH change, but also much more N-def, and the wood will break down very quickly compared to a log.
Pine typically rots in the ground relatively quickly. Much faster than cedar, not as fast as mulberry, willow, or cottonwood. Use it!