Why not give tentative points for translations immediately then finalize translation scores later after receiving enough ratings?
That way, learners get instant feedback and can try to achieve a certain number of points every day. The UI could make it clear how many of your skill points are tentative.
Seems tricky to execute? So you'd lose points if your translation turned out to not be very good? Though as someone who also aims for a goal of hitting around 100 pts every day, I agree that it would be very nice to get translation points faster, like within 12 hours. Not sure how long it takes now? Does it depend on how long until you get enough ratings?
Another possibility is to show you the number of potential points that you could get from sentences that have not been graded yet. So these would be "potential points" rather than "tentative points". The UI could show total potential points right beside your skill points and also in the weekly progress.