Is it safe to take a 10mg buspirone and 50mg trazodone tablet together at night? my son has difficulty sleeping at night. but i've been reading that you should never take the two together?

You are correct, not wise to take Buspirone & Trazodone together. It can contribute to serotonin syndrome when taken together. First, one might ask if your son has talked with a mental health provider as to why he is having sleep difficulties - albeit it is common. He can review his sleep cycle, his activity level, his stress or anxiety level, is he depressed, etc a therapist can be very helpful.