I think this issue is serious and difficult. Right now, I am worshipping at a parish that belongs to the Autonomous Orthodox Metropolia in Western Europe and the Americas, or Milan Synod. In my parish, indeed, all people except my wife and myself are converts from Anglo-Catholicism and trace their origins back to either English or Scottish ethnicity. Of course, all services are in English, and there is almost nothing "ethnic" in them (except that numerous names of old English or Celtic saints are being mentioned - something that you would not hear in a Ukrainian or Russian or Bulgarian or Greek Orthodox church). Even though I am a first generation immigrant from Ukraine and clearly a Ukrainian, I, actually, do not mind that. To me, church is not a social club and not a place for cultural development. It's Church. I am not there to celebrate my Ukrainian identity or to keep in touch with my authentic Ukrainian culture - I am there to worship, to participate in the "leitourgia" together with other human beings, who are of whatever ethnic or cultural or linguistic identity.
On the other hand, at home, I always pray in my native language, in Ukrainian. I cannot imagine for one split second that I will be standing or kneeling in front of Holy Icons and speak or whisper in English. To me, that would be... sorry for a strong term, perverted, un-natural. And, honestly, when I am participating in the "leitourgia" at church, and repeat words and sentences in English, every now and then I do feel like I am missing something. I do miss a priest and a deacon saying and chanting in Ukrainian...
How will it be for my daughter, if she ever becomes Orthodox? I do not know. She came to the US when she was only six years old. Right now, she is a Ph.D. student at Harvard and, of course, her English is very rich and she uses it like a person would use this person's first, native language. Yet, at home, with us parents, she is Ukrainian, and when it is about some very basic things like spiritual convictions, faith, - her language, I believe, is Ukrainian. If she ever becomes Orthodox and comes to an Orthodox church where everything is in English, will she be able to experience the "leitourgia" fully? I don't know... Her chidren, most likely, will be, but is it good? I don't know...
I have some friends who are second and third generation Ukrainians and who very strongly oppose the idea of creating an "All-American" Orthodox Church. They are staunch, enthusiastic supporters of preserving their own Ukrainian churches. They say that "anglos" simply lost ANY ethnicity, the mere idea, the mere basic notion of ethnicity, having actually dissolved in an artificial "plastic" surrogate pseudo-"culture" of the contemporary North America. And they don't want to sink in this ocean of "un-ethnicity" at all.
Again, tough issue and I don't have any answers.