I do not give my dogs annual boosters (vaccinations), can they still be a Therapy Dog?

Yes.  We follow the World Small Animal Veterinary Association (WSAVA) guidelines that state that dogs should not be vaccinated more frequently than every 3 years and only then by challenge (blood test).  We will accept titre tests or VacciCheck as proof of immunity and wormcount.com (or similar) as proof of anti-parasitic care.