WOW, what a ruff deal?! we had just the opposite experience.
our 5 yearold just started kindergarten and is learning german with the swiss german mates (because they also consider it to be a foreign language...) they are 5 in class with limited or no swiss german...
what helped us a lot is picture dictionaries and also cartoons...his 1st german was from mickey maus wunderhaus...and i spent quite a lot of time translating and helping through reading etc.
maybe also try some games? and dora has quite a few cool toys etc. from eng to german and back again