Family i94 extension is NOT needed if its already valid
Your husband and son do not need a new i94 if their i94 is already valid. At checkpoint, they can just show their current i94 - that’s perfectly acceptable.
Family can cross border and get new i94 - Your choice
Although its not required but if you are asked to cross border and you want your husband and son to be with you, while crossing border, they will also get a new paper i94 when they enter US.
Checkpoint at Laredo TX border - 28 miles into i35 North
Yes, there is a checkpoint (called inspection site) while you are coming back from Laredo, TX border around 28 miles while traveling on to i35 north.
They do check your i94 and legal status in USA papers.
So, important thing to remember is to carry i797 approval original (for all 3 of you or whole family).