WOW! Great combination!!!
O.k. your best bet is to speak your mother tongue with your dd/ds. Or in your case... which language you feel most comfortable with except for English.
Is DH first Afrikaans or English? If Afrikaans he can speak it to baby.
Don't worry if the baby doesn't get exposed to English first off as it will get to hear it in playgroups, when you're talking to English speaking friends and later in nursery/pre-school.
I am German and speak it to dd and ds. DH is a Kiwi so he speaks English to them. My family if visiting speak German to her.
Not sure which languages she hears at the childminder beside English as she sometimes comes out with the cutest words and I've got no clue what she's on about. CM and family are Pakistani. One of the kids there is 1/2 Italian so teaches dd the odd word... like the other day she came home telling me '[friend's name] told me to manga!' (btw dd is a very bad eater )
Oh and don't worry about your DH not understanding the other languages you can speak to baby... he'll pick up the important vocab soon enough ... as soon as I mention 'Windel' (which is nappie] dh does a runner