No you will not lose your iCloud details.
If you are getting another iPad and want to give the current iPad to your wife, you can erase it and it will have no bearing on your iCloud account at all.
You contents are stored in the cloud - that's the idea behind it. If you buy three more iDevices, you can download your contents from iCloud onto the devices - even if you erase the first iPad.
You should backup your iPad one last time and then erase it and give it to your wife and she can set it up as a new device with her own Apple ID if she has one - and then she can make the iPad her own with no ties to yours.
How to backup and restore from a backup
After you have backed up the iPad one last time, you can go to Settings>General>Reset>Erase all content and settings and then your wife can set up as new.If you are also syncing with iTunes, the process for you will be a little different. You will need to transfer purchases, backup and sync one last time with your current iPad before you erase it. If you have any other important files, you may want to transfer them to your computer as well.Transfer purchases.Then when you set up the new iPad, you can restore from the iTunes backup, and sync with iTunes as well to move all over your media over to the device.