Speaking to my boyfriend in Japanese: Dinner

Do these sentences sound natural?
いっちゃんがもう夕ご飯を食べたのかしら

一緒に食べましょうね
or
いっちゃんは一緒に食べたいの？

もっとご飯欲しいの

いっちゃんはもっとやって欲しいの
or
いっちゅんはもっと欲しいの

So your Japanese boyfriend’s nickname is “Itchan,” and you are talking face to face with him? What age are you two? The sentences you have got sound… quite childish,, or mother talking to her child.

1. If you want to ask him if he’s had dinner already/yet, then it would be:
いっちゃんは　もう夕ご飯食べた？
Or
いっちゃん、もう夕ご飯食べた？
(Your 1st sentence sounds like “I wonder if Itchan has eaten dinner yet,” just talking to yourself.)

Between your 2nd and 3rd sentences, that depends on what you “want to” say.
2. Says: “Let’s eat together” “We will eat together, shall we.” (in a somewhat motherly tone, though.)
And 3 says “Do you (=Itchan) want to eat together?” (implying “I want to, but what do YOU want to do?”)

4 sounds like a mom asking if her child wants another serving of rice.
5th one is a complete no-no. It can sound like something else totally.
If you are asking him it he wants to eat more (of something right in front of the two of you), I would say
いっちゃん、もう少し食べる？

４コママンガ。。。

I agree with AK (and also to the other poster ;), and the reason it sounds like a parent speaking to a toddler is because it sounds like the person is speaking in behalf of someone who find it hard to speak up. Typically, a man old enough to be a "boyfriend" can speak for himself even without being asked, or he can accept straightforward "questions" without having them sound like "suggestions".

But it is indeed common for a boyfriend to want to be baby-ed or spoiled. Or the boyfriend might happen to have physical difficulties and cannot speak. You never know how boyfriends and girlfriends speak to each other in their private hours. And one would assume that by the time she says the last two lines, they are no longer in the dining room.

I talk a bit childishly to my boyfriend in English because he seems to find it cute. I am not sure how that translates in Japanese. I am 21 and he is 25, but he says he sometimes forgets I am younger since I take care of him so well. I don't want to sound like a mother, but I am also a bit shy. So sometimes I won't ask directly if he ate, but will say to him in English "I was wondering if Icchan ate dinner yet?" I do call his name in public though, but in public I would still probably word it similarly since I am not a direct person. Even before we were dating, I could only speak informally most of the time since I did not learn Japanese in a school, but from my Grandfather who is Japanese.

Informal speech is fine. That’s not the point. Being shy might set the tone for the way you speak, that’s fine. I don’t know in what kind of family background you’ve grown up, so maybe that sets the tone too.

I guess in English “I wonder if you ate dinner yet?” can sound pretty matter-of-fact, but (at least to me) using the nickname (particularly with “-chan”) as the subject of the sentence and saying the same phrasing in Japanese definitely sounds, well, motherly, as the one who takes care of the other one who cannot speak for himself.

So… instead of saying “icchan wa…?,” I would suggest just asking the question addressed to him. もう夕ご飯食べた？ for example. Because the word “you” is not explicitly in it, it will sound softer (meaning less direct, less pointed) in Japanese anyways. Calling him by the name is OK, just like you might say in English “Ken, have you eaten? Instead of “I wonder if Ken has eaten.”

So:
いっちゃん、もう夕ご飯食べた？
いっちゃん、もう少し食べる？

Thank you AK and Uco for your help! I understand a bit more now.