iCloud Storage of Photos on all devices with latest Yosemite update

I just completed latest software update on my iMac and have the new Photos app replacing iPhoto in my doc. The option to use iCloud storage so I can see all photos and videos on my iPad and iPhone came up so I decided to use it since my iPad and iPhone only have the 16GB storage on the devices. They are both older, 2011 and 2012. All my devices are updated and I have enabled iCloud drive on them as well as enabled for the Photos app and some other things like mail and calendars, etc . I had to purchase extra storage for $.99 a month for all the photos (5000+) on my iMac. So none of the photos are showing up on my iPad yet. I haven't tried to set it up on my iPhone at this point, just thought I would start with iPad. I am at home so all devices are using Wifi. So my question is: does it take a long time for the photos I have on my iMac to show up on my iPad or do I need to do something else? One other item of note: my iPad does seem to be slowing down these days and it takes some apps such as my calendar a while to open anyway so I wonder if that is part of the issue. Thank you.