5 week old kittens still aren't eating solid food

I know they haven't attempted to eat any wet food & pretty sure they haven't eaten any dry food (I keep a bowl of it in their pen because momma kitty doesn't like to eat outside of their pen). They're been drinking water since last week, but the most interest they show in food is watching momma kitty eat. Is this normal? Is there something I should try to encourage weaning? 

I start out by making a gruel of wet food and goats milk so that it is soupy. I then dip my finger in it with the kittens near the plate. I hold my finger up to the mouth and put a little on the lips so they lick it off. If they show interest, I slowly move my finger down to the plate so they start licking the gruel. Remember though, kittens develop at their own pace. I have had some show interest as early as 4 weeks while others still were not really interested until after 6 weeks. I don't force weaning because my kittens don't leave until 12 to 16 weeks old.