My husband just got diagnosed with strep throat. We have 1, 3, & 5 yr. Old kids. Should I be concerned about them & what can I do to protect them?

Variable risk. Your husband has been contagious from some point before symptoms started to 24hrs after starting meds. The quoted attack rates in families range from 1/32 to 1/4 so monitoring everybody is reasonable. Good hand washing & avoidance of oral contact is key. Also monitor symptoms & have anyone with a fever tested for at least the next week.
Good hygiene. Strep throat is a bacterial infection which is transmitted by oral secretions. To avoid spreading the infection, make certain your children (and you) do not share food and drinks with your husband. Same thing goes for kissing for now. Generally, after a person has been on antibiotics for 24 hours and is fever-free, they are not contagious. See the doctor if the kids get sick. Good luck!