Yes. Although probably it is Yanda.
Yes - 用 here refers to some errand or something that needs to be seen to.
Yes. 来ない becomes こねぇ and って is quoting. It is kind of a rude way to say you aren’t coming and Jumbo then criticises him in the next speech bubble. Yanda is a recurring character and arch-nemesis of Yotsuba later in the series.
Yes.
し＋な (if it still doesn’t make sense then ask but probably that’s enough information for you to work it out on your own which is probably more useful, I hope)
Did my first five sites yesterday too. The only part I got a bit confused was
とうちゃん手がはなせないからな俺の分もよつばがふってくれ
Just because I didn’t know exactly which はなす they mean… And didn’t think of the 放す one.
Thank you very much. Yanda, of course, あいつだめだわ！, (he’s no use, that one!).
It would be the し of listing reasons and the な particle commented above, similar to ね but more about the speaker’s own thoughts about the situation?
So it’s like とーちゃん is thinking out loud that ジャンボ already did quite a lot of work (the part of two people). To which ジャンボ replies “That’s not so, I’m not doing anything!”.
Looks like this ジャンボ character is quite a nice fellow. And tall too, more than one head taller than とーちゃん!
Or is the implication that he can work for two since he has gotten so big, according to Yotsuba?
In page 12, middle section, right-hand frame, ‘そこおいといていいぞー’:
In page 13, when ジャンボ uses は in ‘いや おまえの嗜好はいい’, is he implying something, like there are other qualities that are not いい?
Really it could be either, but going off the context the likely translation is that because the other did not show up, ジャンボ can do the work of both people.
てもいい usually implies that ‘from several different options, (A) is fine’. Not including the も refers specifically to one action. So the difference between the two would be this.
そこおいといていいぞー ‘Putting it there is fine’
そこおいといてもいいぞー ‘Putting it there (as opposed to doing something else with it) is fine’
Really this nuance difference is tiny. So in most cases も just makes it sound slightly emphatic 
Yep. Anything that can be dropped will usually be dropped 
I interpreted this xはいい as とうちゃん not caring/dismissing what ジャンボ likes as a suggestion to bring something less weird than pudding. It could be ambiguous, but the いや at the beginning reinforces the “not caring” intepretation I think.
This sounds right in this context… quite tricky because it’s the opposite of what I first thought (something along the lines of “nah, your taste is good” = choose whatever you like)
I’m not having any luck with this bit:
Thanks for any help!
My understanding is:
おねーちゃん - casual form of big sister (お姉さん - おねさん) which is commonly used by younger girls to refer to older girls
手えふった - another form of waved? (手を振った - 手をふった）
Big sis waved at me.
If anyone thinks otherwise, please correct me!
Yes, that’s correct. She said:
“She waved at me.”
“Dad, you do it too.”
Great, thanks, that was a two-fer. I thought the dad’s name was とー. 
Haha! Yeah, she’s just not including the honorific (お)父さん.
The え sound in 手 is simply the sound being extended due to her childish speech, as well as her simply skipping the particle. ふった is just past tense of 振る, to wave, but again, because she is a child, often they will write hiragana instead of kanji to represent the more childish language/knowledge
Ah! That makes sense! Thank you so much! It’s especially helpful to understand more the nuance around childish speech.
I’ve got a bit of a question as to the dialogue on page 11.
よつば says to ジャンボ「またおおきくなった」and ジャンボ follows it up with a response that I believe means ‘Where’d you learn to speak like that?’
Given the vocab card for 股, I’m assuming her sentence was interpreted as like ‘Your crotch is so big!’
Is this a play on words where she is meaning to say something like ‘You’ve gotten even bigger!’ and it’s interpreted dirtily or is it just a ‘kids say the darndest things’ kind of moment?
Thanks!
I think that また is simply “again”
“you’ve gotten bigger again”
Call me immature, but I had a good chuckle at that incorrect vocab in the deck and how it changed the meaning. I just fixed it!
This また is また with the meaning of ‘again’ or ‘furthermore’. ‘You got bigger again!’
Given his reply of ‘Where’d you learn such a phrase?’, I believe he is referring to the 見ないうちに ‘when I hadn’t seen you’, as it is a little bit difficult grammar for a child to use. That was my interpretation of what he was referring to at least.
Looks like you already corrected the 股/また issue 
