No, it should not be an issue. The routers can easily address 100+ devices on the network. The part where you start getting into trouble is bandwidth. Your network is only as fast as the slowest component. That would be your connection to your ISP. For me my ISP runs at 20 Mbps which works out to be 2.5 MBps (notice the difference, Mb-Mega bits, MB-Mega Bytes, 8 bits = 1 Byte)
Now your router most likely can do 100 MBps accross the network plugs, which means that all of your computers hooked to your router will be able to communicate and transfer at that speed, but when connected to the internet they all share whatever limited bandwidth you have there, so Inet may get slower as you have more devices trying to access it simultaneously (depends if you're just browsing, streaming movies, or playing games).
Within your router all of your computers will speak to each other quite quickly, but once you get a lot of them going things may slow down a bit with increased traffic. But you are not likely to experience that with a small home network like yours.
An example that I would like to share, is that when my wife and I first got our house we initially went with the cheapest package that our cable company offered for Inet which was 7 Mbps, and when I would be playing Diablo II online and my wife would be browsing pictures on the Inet I would get lagged out of my game quite often. Once I upgraded to the higher bandwidth I had no problems and was even able to have 2 computers on Diablo II while my wife was browsing pictures.
So, if you want to skip all of the stuff above, the short answer is Yes you will be fine and have no issues.
