Android - Is it a good idea/useful to use two Anti-virus apps on Android?

No. I'll even go to the extent of saying using an Antivirus is of no use if you only install apps from Google Play.

But if you install apps from third party sources (i.e APKs, etc.), using an antivirus might actually make sense. But using 2 AVs doesn't make sense in any scenario imho.

A known issue with running 2 AVs is that they'll consider each other as a potential virus.
This has to do with the behaviour of these programs. They scan directories, perform root-operations (if you have installed the AV on a rooted device), and so on.
This is true on any system, not only mobile devices.

You can in most cases run an AV together with an anti-malware product.
I do say in most cases.

As mentioned by Karan, there is no real need for AV software as long as you only run Google Play / Appstore apps and you don't download any rubbish from sites you visit.
Do keep in mind that there are some dangerous apps on Google Play. I'm an Android user myself, definitly no iFanboy, and I must admit not all Play apps are safe.
So always check the permissions and intentions of an app before installing it.

I myself have Avast! Mobile Security on my tablet.
This is because I run some off-the-market apps. MS also allows me to protect some apps with a pincode, such as my email apps.

I don't think running an AV is a waste of resources, but if you handle your device with care, there is no real need for one.