Since we're crossing by land but flying within Mexico, we'll each need our valid, current passport book and an FMM form—I've included some helpful links below!
https://travel.state.gov/en/international-travel/travel-advisories/mexico.html?gad_source=1&gad_campaignid=44031958015&gbraid=0AAAAAqbBk5urzwdCQS5yCEuUI4g8pNJrr&gclid=Cj0KCQiAo4TKBhDRARIsAGW29bc8faNR5i9NaZfi6HnBcymjlhk9xTnAQNWUHzkY8XGf8s0-6TGnQ-0aAuhaEALw_wcB#entry-exit
https://www.inm.gob.mx/fmme/publico/en/solicitud.html