Have you tried this "fix"? Experimenting with the date in the settings?
Go to Settings>General>Date and Time>Set Automatically>Off. Set the date one year ahead. Try to update the apps again. If you get an error message, go back to the settings. Correct the date and time (set automatically) then go back and try to update the apps again.
The Complete Guide to Using the iTunes Store
Can't connect to the iTunes Store
iTunes: Advanced iTunes Store troubleshooting
Best Fixes for ‘Cannot Connect to iTunes Store’ Errors
Try this first - Reset the iPad by holding down on the sleep and home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider - let go of the buttons.
This works for some users. Not sure why.
Go to Settings>General>Date and Time> Set Automatically>Off. Set the date ahead by about a year.Then see if you can connect to the store.