Parents can help their children learn foreign languages even if they are not English teachers and even if they think that their knowledge and pronunciation of English is poor. If you try to teach your children English, you do not need any special course but basic knowledge and some expressions and sentences. You should not try to teach them longer than 10 to 20 minutes, once to three times a week. It is important to repeat words but it is not necessary that your child understands grammar.
When teaching your children English it is very important that you do not laugh at them if they pronounce a word in the wrong way. Never say that they do not have talent for languages. Encourage them if they cannot remember words immediately (this is quite normal). Do not compare them with other children by saying that their friends speak English excellently.