If you want to go on and subsequently produce newsletters, posters and so on then use InDesign, but it may be a steep learning curve.
For small job alternatives, Illustrator or Photoshop
Otherwise use MSWord for ease of use.
The best Adobe product for that would be Illustrator
I think duplexed output would be simpler from InDesign which is more suited to multiple pages than Illustrator.
Hi Gary - Either Illustrator or InDesign will be very capable for your flyer; the choice comes down to which you are more comfortable with. I use Illustrator when the layout is more free wheeling, because I find Illustrator easier to "Play" and go crazy. Depending on your church, that might be desirable or not!. InDesign, IMHO, is better for more structured, multipage documents especially where you have copy that flows between columns, text wrapping around pictures. If you plan to use the flyer as a template for future publications, that gives InDesign an edge.
If these products are both new to you, pick one and do a tutorial; like everything Adobe touches, they err on the side of complexity to achieve completeness. That means the learning curve is lifelong. The good news is, it is much easier to learn when you have a project to accomplish, so your flyer should be a great way to get up to speed.