please help with this translation

can someone help me with this?
あいつがせっかく勇気出して誘ってくれたのかもしんないのに...やっぱあのタイミングで行くべきだったか...
何時ってくんだろ...
??

I'm no expert on colloquial Japanese, but since noone else has chimed in, I'll give a rough, translation:
"they'd finally gotten the courage to ask/invite me... I guess I should have gone when I had the chance...
What time are they coming?..."

Not sure who "they" is. Hopefully the context will make it clearer for you.

As for the last line... Maybe I'm being dense, but I'm not so confident about the intended meaning. "って" denotes something said, or a quote, and "んだろ" is basically like "right?". "く" might be from "くる", to come, hence the translation above.

He might have gathered up his courage to invite me out... maybe I should have gone at that timing after all...
(The last part I cannot figure out; too colloquial or wrongly written.)

Oh, thanks!
And I just noticed it was the wrong kanji, sorry, actually is "何持ってくんだろ" so I guess the person is wondering what they are going to bring with them?

Also, if it's not too much to ask, these two sentence:

"いつの間に？" I know this mean 'unnoticed' or before one's noticed but it confuses me the "?", it changes something as a question?

And "いやいや、そうでなく... もらったんだから好きにしていいだろ？" this is after someone says "あなたも私の写真あげるから" what it means basically the person can keep their photo too, right? Well, I mean that they are giving it to them too...

If it was 何持ってくんだろ？ then yes, it's "I wonder what they/he is going to bring?"

いつの間に？ is like "When in the world did tat happen..? (while I didn't notice)?"

"あなた（に）も私の写真あげるから" I will also give you my photo too...

"いやいや、そうでなく... もらったんだから好きにしていいだろ？" No, that's not what I mean. Since I got it (from you), I can do whatever I want to do with it, right?

Thank you!