If wifi is your only option, is the 25m open or how many walls etc does it have to pass through? The medium that the signal passes through has to be taken into account as well, if its stud partition or block wall and so on. 5ghz has less penetrating ability, but is less susceptible to interference, although 2.4ghz is fine for a camera. I'm a bit out of the loop with consumer wifi but I've had good success with Asus routers (can be configured as extenders). I'd start with one and take it from there.