I am probably in the minority, but leaving things well enough alone was pretty much my motto for K and 1st grade. I don't think that it has harm either DS9 or DD9, who are now 4th graders, and who have moved further and further ahead of their peers as time passes.
I don't think that you are in the minority. I was blissfully unaware that all of the differences in my dd14 were due to giftedness in K and didn't figure it out until someone suggested it to me when she was in 1st. We had issues in K, but they were more related to her intensity than anything else. One that comes to mind was a writing project that the K teacher gave the kids where she passed out prompts and had the kids each write a few sentences about the topic. The quality of this writing, of course, varied. The problem dd ran into was her being convinced that the teacher intentionally gave her a prompt that involved something like a hunting situation. Dd is vegan (she was vegetarian at the time and vegan now). She wouldn't let go of the idea that the teacher was intentionally antagonizing her and wrote something that involved an animal rescue organization rescuing the animals.
Academic challenge wasn't a big concern of mine, though, early in elementary. I started to get concerned around 2nd-3rd grade when it became clear that she was learning nothing and work ethic was suffering. Her 2nd grade teacher was awesome, but without a really motivated teacher, we were in trouble.
That was the point where we really started to make an effort to do something different: GT pull outs, subject acceleration, and then a grade skip at the end of elementary.
eta: I should mention that none of the stuff that we did later was even available before 2nd grade anyway. Dd was one of the few kids who was formally ided as gifted in 2nd grade b/c the school didn't test usually until 3rd (we had private IQ and achievement testing done in 2nd).
The only thing we would have been able to get in terms of additional challenge in K or 1st would have been skipping a grade sooner than she did and I don't think that I would have done that so early in elementary for a few reasons. One was that she was very young for grade anyway and the other issue was that I was more comfortable seeing that she was continuing to pull further and further ahead academically to the point that there was really no way for her to learn in any subject in the grade she was in. I would have worried earlier in elementary about her long term trajectory, but I'm sure that there are kids out there for whom it is obvious that a skip is needed sooner.
As you mention, with the foreign language issue, I can't see skipping right now in your situation, but perhaps it will be a good choice later once your dc is more fluent in the 2nd language. Perhaps there will be alternate means of challenge, though, as well that don't involve skipping a grade or subject acceleration.
