Frankly, I think the 357 Magnum loaded with a heavy 180 grain hunting round would be a better choice than the 45 ACP, you'll get much better penetration from the smaller diameter faster round.

I would also suggest a 4 inch gun as apposed to something shorter. With the right holster it's possible to conceal a 4 inch revolver without much problem. If you want one example of how to do this, just watch Dirty Hairy again. Yeah, you'll have to commit to wearing some type of cover garment but even a light windbreaker will work and if you make it a habit for yard work nobody will really notice. If anyone asks, just tell them your allergic to bee and wasp stings and the windbreaker is just for a bit more protection.

BTW, I understand why you don't want to carry openly, IMO Open Carry is an invitation to a burglar, especially with some of today's teenagers.