No. TD carries no work authorization at any point, and a delay does not create a temporary permission. She may study, and the children may attend school, but employment of any kind inside the United States requires her own status that permits it.
TD permits study and residence, never employment
Derivative TD status exists only while Oluwaseun holds TN, and it authorizes no work. His wife could not take a U.S. job, freelance, or continue working remotely for an Ontario employer from inside the United States.
That restriction bites hardest during a delay, when a household has moved on one salary and the second earner is idle. Two further details matter for planning. The relationship must be a legally recognized marriage, since a common-law partner is not a spouse for these purposes and would need a separate route.
A child ceases to qualify for TD at 21, so a household with an older teenager should map that birthday now rather than at renewal. Where the second income is essential, compare TD against the L-2 and E-2 spouse rules, under which a spouse is employment-authorized incident to status.