Create a limited wireless subnet for the i-Devices that only has access to specifically what they need to use these applications. After doing that, you have nothing to worry about as far as security goes.
As an aside, I should say that if you think your network is "secure" just because you use WSUS and a centrally-managed AV system, you're having the wool pulled over your eyes. While doing these two things is a very good idea, and will go a long way to improving the security and stability of your network, there are many more things that you ought to be worried about. Honestly, the presence of a few iPads should be the least of your worries if you have the network itself locked down appropriately.
With all due respect, I feel like you have a bit of FUD with regards to the iPad and the "security" thereof. Apple has released tools to help with the configuration and management of IOS devices. No, you won't be able to deploy updates via WSUS or policy via GP, but honestly that should be the least of your worries. Due to the code signing and vetting process that apps go through, it's quite difficult to get viruses or malware on IOS devices, especially if you firewall your network in such a manner that they are not able to access the internet (or at least only access a small subset of the internet).
Think about this for a moment: many hospitals and clinics are starting to use iPads as an interface for their electronic medical records systems. With all the laws surrounding the need for security of personal medical data (HIPAA in the US, other laws elsewhere), it's clear that IOS devices certainly can be locked down appropriately. You've admitted you're not familiar with the devices. That fine. I certainly understand being hesitant to adopt a technology due to unfamiliarity. However, don't use the "insecure" buzzword as your stated reasoning for avoiding these devices. Just admit that you're unfamiliar and that perhaps that the management should purchase you an iPad for testing purposes so you can increase your familiarity and trust of the devices.