Are chain ring spacers a good solution to adjust chain line?
Yes spacers are fine for this. It sounds like you want to move a few millimeters - 2 or 3 millimeters is fine and the bolts can handle it. 

A word of caution about bottom bracket spindle: make sure that your crank is clearing the chain stay. Inspect this under load. You might look and think you have enough room for the shorter BB but on your first ride you can put a few nice gouges in your chain stay when you put the hammer down.