Some servers (mostly POP account servers) only allow one connection at a time.
To prevent the iPad from hogging that connection, go to Settings > Mail, Contacts, Calendars > Fetch New Data > Advanced: Selectt the problem account and change it to Manual.
This will make sure the iPad is not periodically connecting to the server. It will only get mail when you actually open the Mail app, and when you tap the refresh icon at the bottom of the email list.
The server should automatically time out the iPad's connection. This typically takes about 15 minutes; so you may not be able to just jump onto the laptop right after using the iPad. But since the iPad is not connecting every 15, 30, or 60 minutes; the server should be available most of the time.
I'm not that familiar with Charter; but if it offers you the ability to set your account up as IMAP or Exchange instead, this would bypass the problem.
It's also possible that somewhere in your email account options (at charter) you can increase the number of simultaneous sessions for the account. That would also cure the problem.
