There will be some additional latency but it should be almost negligible compared to your total ping.
This is the most accurate straight-forward answer so far.
OP, assuming you have a decent router that's properly configured and within range, it shouldn't cause any problems. The additional latency experienced using WiFi as opposed to wired is VERY minimal, and won't be the biggest factor in determining your ping.
I've been gaming on a WiFi connection for years now and it's been very solid. I have very reliable PCI wireless adapter in my computer, which communicates with my trusty old WRT54G router downstairs. (There was one time when my wireless connection kept dropping every time I entered a game, but it was because of an outdated driver. I updated my wireless driver and I was good to go.)
I can always join TF2 servers where my ping is <100, there are even some servers where my ping goes <50. But, that has more to do with the server itself being on a really good connection. For example I remember being on one server where I had a ping of 30, and when I checked the scoreboard, seriously all of the players had a ping <50 so it must've been a really good server.
Anyway... while wireless internet CAN cause issues, if you have it properly set up and don't have any kind of crazy interference then you should be perfectly fine.