What would you need if the roles were reversed? A day after a surgical procedure (with a six week recovery time) while married, the former spouse left for a two week business trip. It happened often. I called in the help of friends since I, too, was without anyone 'here'.
Would you make an offer to assist with time with the kids and return them at night?
Allow her to make her own decisions and decide if she really needs your help or not?
Parenting is a worrisome time with or without a nuclear family. The kids will not wither away and die while they're with their mother.
In the end your worry is presumptive and controlling. You are deciding that their mother is incapable in caring for her children when she is not 100%.
Let her make her own decisions, not what makes you feel better to ease your assumptions.
