Assuming that you have the right BB for good chainline and that your cranks are in good shape, don't sewat moving the cranks over. The only material difference between 9s and 10s cranks and chainrings is the separation of the chainrings which is narrower for 10s matching the narrower chain.
Often 10s chains run fine on 9s cranksets, but just as often problems occur with the chain hanging between the top of the inner and inner face of the outer ring on down shifts.
If that's a problem you need to narrow the gap. Some companies do this by milling a bit off the inner face of the outer ring where it bolts on so it moves inboard a bit, others narrow the section of the spider between the rings for the same purpose. Check with various companies to see if they offer rings with the 9s/10s conversion built in. If not you might try thinning the tab, but I warn you it's a slow process and difficult to do well without decent hand filing skill.
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