I take it you're referring to the ability of the rods to be moved front and back a little bit. That is normal.

Checking for excessive wear by jiggling by hand doesn't give good information. It also doesn't tell you diddly about what the bearings and crankshaft look like. The only way to inspect is to remove the caps, look, and measure. Since you describe a mild tapping, you'll probably see some bearing color from wear.

Main bearings can be done in the vehicle, but it's not easy and generally not worthwhile. You can undo the caps, but working the top half of the bearing in and out is not fun.