So the issue with a single flat network like yours is broadcast traffic, just noise on the network. This is not a massive issue on the wired network, but on wireless it can chew up a ton of airtime and cause your wireless network to perform badly. Segmenting your wireless network into its own broadcast domain can make a huge difference, as it stops traffic from spilling over from the wired clients.
That said, this really depends on how many clients we are talking about. If your entire network consists of less than 100 devices (wired and wireless), then it's probably not an issue, but you are talking orders of magnitude larger than that, it maybe something work looking into to.
Personally I would do it as a matter convention, and a way to clearly identify wireless clients from wired ones when looking into things like logs (ie if every wired client was 10.10.x.y and every wireless client was 10.20.x.y, it makes identifying where things are coming from quite a bit easier).
But keep in mind you'd want to do more than just setup a second IP range, you'd want to break up your network into VLANs, at least one for wireless traffic and one for wired traffic, this essentially segregates them, and allows you to create access control and routing paths between the networks for better and more secure management overall.