Contrary to popular belief, the CBP can grant a new 90-day admission, if it's obvious that the person's not gaming the system to live in the US. 2.5 months in Mexico ought to suffice for that.

However, if exiting the US by land, seek out the CBP (it can even be the entry checkpoint) to have the exits of your wife and children electronically recorded in the electronic I-94 system.

Contrary to popular belief, the CBP can grant a new 90-day admission, if it's obvious that the person's not gaming the system to live in the US. 2.5 months in Mexico ought to suffice for that.

Since you're a US citizen, there's no limit on how long you can stay in the US. You're supposed to use a US passport to enter and exit the US.

Contrary to popular belief, the CBP can grant a new 90-day admission, if it's obvious that the person's not gaming the system to live in the US. 2.5 months in Mexico ought to suffice for that.

However, if exiting the US by land, seek out the CBP (it can even be the entry checkpoint) to have the exits of your wife and children electronically recorded in the electronic I-94 system.