For running air tools you'll need lots of flow(CFM)& the appropriate pressure (PSI) and the scuba tank won't get you that.

Your best bet (for the $$$) is to buy a 5-15lb liquid CO2 tank & regulator. Total cost will be about $120-200 depending on whether you buy new or used then simply fill it as needed. My 10lb tank cost me $9 for each fill. For more specifics check the powertank site.

Alternatively you can spend $400 or so on a high output 12v compressor (both CFM & PSI) to run those tools.

Last but not least, you can buy a 110VAC compressor & tank at any tool place and buy a properly rated 12vdc-110vAC converter. Will probably cost in the neighborhood of $300.

HTH!