Yes. An E-2 spouse is employment-authorised incident to status and may work for any employer or in the enterprise itself.
Spousal employment is available, and it interacts with the marginality argument
A spouse admitted in E-2 dependent status holds employment authorisation by virtue of that status and may take employment without a separate grant of permission, although employers may ask for evidence. Children may study but not work, and dependent status ends at twenty-one. For a small consultancy there is a point worth thinking through.
A spouse's outside earnings support the household but they are not the enterprise's income, and marginality is assessed on what the business can generate, not on total family income. Meanwhile, if the spouse will work inside the business, describe that role consistently with the control story told about the investor, because a file that appears to give operational direction to two people without explaining how is a file that reads as unclear on the one point the classification cares most about.