MacBooks and iPhones not staying connected to wifi.

Question

When Yosemite came out I downloaded it to my Macbook Pro with retina and I've had no problem with it. Now when I did it to my dad's non retina Macbook Pro, he seems to be having trouble staying connected. Whenever he's online he keeps telling me he keeps getting booted off and has to go and reselect the wireless only to be kicked off again. As of lately that same problem has carried over to my iPhone and sometime it will jump back on the wifi or it will eventually prompt me to select the network again and it will reconnect. I'm not sure why this is doing this all of a sudden and wonder if their's any solutions. Also, I have another question up following the same type of question but it has to do with the wireless and I'll leave that down below. But I wonder if it's too many devices? There's my iPhone, my mom's iPhone, her iPad, my Mac, my dad's Mac, his phone, his work laptop, an Xbox One, a PS4, and possibly his cell phone. You could say we're pretty connected. Out of all those devices connected, only my mom's iPad, my phone, the Xbox and PS4, alongside my dad's Mac are the things mainly being used. The other iPhone and work laptop and cell phone aren't on the network frequently and are usually in sleep mode, if not turned off.

Answer 1

Try the basics first:
Change your router channel number.  Most times this works & is all you have to do.
Disconnect & reconnect your modem.  unplug it for about 10 seconds.  Plug it back in.  Do the same for Apple’s routers.  Wait for everything to reboot.
System Preferences>Network
Click the Assist Me button.
In the next window that pops up, click the Diagnostic button & do the necessary.
http://support.apple.com/kb/HT4628 Wi-Fi: How to troubleshoot Wi-Fi connectivity
What to do when you can't connect to the Internet
OS X Yosemite (10.10)
Conflicting info.  Your post states OS 10.10.1.  Please correct your system profile.  Thank you.