icloud notes not fully loading on ios 8.1, OSX Yosemite & icloud.com
OS X Yosemite and iOS 8 have changed the way iCloud syncing works. With the introduction of iCloud Drive the file structure has been thrown open, but devices running iOS 7 or below and OS X Mavericks or below will not sync successfully once you have 'upgraded' to iCloud Drive. Have you done this? If so, the iPad won't sync.

To solve: 
First I would try what tubedogg suggested above, and then I would recommend emailing your critical notes to yourself and putting them in the Notes app in iOS 8 or iCloud.com. See if it syncs, and then I would say it is safe to upgrade to Yosemite.
If it still doesn't work you could always have a go at using an alternative notes service like Evernote or any other which features syncing.

I learned this from personal experience when upgrading to Yosemite iOS 8 and iCloud Drive. Hope it helped! ;)