That's also an accepted answer. Technically the choice is probably taking place in the future even in the Swedish sentence, it's just that our present tense covers more than the English one. But we picked the present continuous for the main translation which at least sounds better than just the present, and is a more literal translation.
Yeah, I get it. I think that the translation in this instance is worded in a way that makes the Swedish structure clear which is the more important part. If you had all these present tense answers and then suddenly BAM this one is randomly in future tense, it would just make it a bit more difficult.
As a native English speaker I would say that even in this context it still sounds a little awkward - almost like a command from an overbearing bystander! Or a noble speech (eg I die for you) that is somewhat ´less noble! A completely acceptable sentence, but still slightly odd. I would say "I'll (I will) choose for you!" I think... Any other native English speakers agree? (Or disagree!)
Edit!!! I completely missed Shnur1987's comment above which says the same thing. Sorry for the clutter!
I am not a native English speaker, but I would translate this sentence rather as "I am choosing in behalf of you". If you say "I am choosing for you", it seems to imply that you select the other person (for instance in a team, for a job, as a partner). Would "I am choosing in behalf of you" be acceptable?
Yes, the past of "äta" is also "åt".
Prepositions are very tricky in translatione even between relatively closely related languages such as Swedish and English. The preposition "åt" is simply the one used with "skrattar".
The preposition is usually used either for the meaning I already described or for implying direction. (Åt höger = to the right)
As given on wiktionary, "dig" and "det" are transcribed respectively as /dɛj/ and /deː/. So, aside from the variation in short and long vowels (the triangular colon indicates a long vowel, see Academia Cervena's excellent video lesson on the Swedish vowels https://www.youtube.com/watch?v=hzYArZVTD4s), I think the biggest difference is that the vowel in "dig" collapses at the end down to a /j/ (the voiced palatal approximant, see https://en.m.wikipedia.org/wiki/Palatal_approximant).