The cause of the crash - between a small liveried Peugeot van and a VW Polo - is unknown and police want to speak to anyone who may have seen either of the vehicles before the crash which happened at about 12.40pm.
The children were taken to hospital with serious but not life-threatening injuries.
A man and woman were also taken to hospital. Their injuries are not believed to be life-threatening.
The road was closed for a short time to allow emergency services to deal with the incident.
Any witnesses should contact West Mercia Police on 101 quoting reference 292s of August 1. Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org