Not really..It should be 我们问一下老师. You can see '问一下‘ as a verb for 'ask'.

Yes, as @Helen said above, Not really. In other sentences, For example ‘这个问题我不会，你可以问他一下’ and '......问一下他' are both okay. Here '一下' is more often used in spoken Chinese. In most cases, if you don't know where you should put '一下', putting '一下' before the object is much safer. Sometimes, putting '一下' before and after the object have a little different meanings. For example, ‘揍一下他’ or '揍他一下'. The first means 'giving sb several punches', while the second means 'giving sb one punch'.

OMG!!!!! after seeing the two answers above, I doubt if I am a chinese!!! plz listen to me. the ONLY problem that you have is that "儿". We cant use "儿" like that, meaning that: 我们问老师一下. is correct --------- at least, for me, it's definitely correct. e.g. - 今天几点放学？ - 我不知道。我们问老师一下吧。 omg..... plz other chinese tell me this is correct..... verb + object + 一下 = verb + 一下 + object 抱我一下 --- 抱一下我 打他一下 --- 打一下他

I think this sentence will be ok in oral Chinese without "儿", sometimes I will also say "我们问老师一下" to my classmates. :)