Is there a problem of yichud with a married woman who will be at home for around an hour in the early evening (for example 6-7 or 7:30) with 2 young boys (ages 10 and 11) that are staying by this family. There are no other children at home and the husband will be coming home later.
If the husband is in town, there is no problem.
Even if the husband is out of town, there is no problem, due to the fact that there are two boys, and one is considered a shomer for the other. This applies at a time when it is not ordinary to sleep; later at night, one shomer is not sufficient.
Note that in principle, yichud applies to children of this age; see Shulchan Aruch, Even Ha’ezer 22:11; Nitei Gavriel 11:1.