I think if the home you are considering is near the proposed complex that you are buying something pretty cool. I would consider how any night lighting might affect your home, and if that kind of lighting will exist at the complex or not.
If you're talking a typical community center, you're not talking a huge sports complex with tons of traffic. Since Safeco Field and the Seahawks Stadiums don't feature fields, trails, state park or a wading pool, my guess is the proposed complex is going to be a pretty fantastic addition to the area. Does the proposal have a website?
If you like sports, people and see yourself using some or all of the amenities, it sounds like a win-win, and an enhancement to the surrounding property values and desireability.
If it is just being planned now, as a general rule, it is a plus.
For example, there is a plan to make many of the reservoirs in Seattle subterranean. Where the reservoirs are currently will be parks much like you describe. Many will have playgrounds, sports fields, off leash parks, etc. My feeling is that it will be a pain in the butt for the next few years until all the work is done, but after that it will be a fantastic addition to the value of the neighborhood.
The biggest effect I see is just the change in the neighborhood. People who like it as it is will be more likely to move elsewhere to capture what used to be. Folks looking for quick easy access to all the amenities will be drawn to the area. The turnover will be ongoing through construction and a few years after.
If you plan to live there through the construction phase, and the new facilities appeal to you and dealing with the building doesn't bother you, you should be fine.
If you need to sell in the midst of the messiest time that could be a problem you would want to avoid. Long term, parks are drawing cards.
Good luck in your purchase.
Or if your house is directly next to the facility, and it there is not a buffer between your property and the complex.
In the larger conxtex, I agree that public amenities add to the value of a houses.
Hope that helps!
I can imagine that if you had a huge sports complex with tons of cars all trying to leave (or get in) at the same time it would be far worse. Think about the traffic problems it will bring with it.