Double Booked

Hi guys, So here is the situation: I had pretty much given up on an internship for the summer because it was mid-may and I had nothing. Now my brother works at some big-name microfinance NGO (charity) and he put his ass(like the whole time I was begging him he was like but I dont want you to fuck it up for me) on the line to get me a job there. Then I get an BO internship at some finance company where I was previously wait-listed.(I am going to be a sophomore). I have an obligation to my brother but I also have this amazing opportunity to work at this finance company. I thought I would just suck it up and overwork myself. I asked the guys how flexible the schedule was and they were like yah man whatever as long as you get your hours in we dont care when or what you do. Little do they know I might need to go in the the NGO quite a bit. (Luckily they are both in LA) My question is how would you guys handle this. (Note that bailing is not an option under any circumstances.) There is a number of scenarios: work weekends at the bank (but IDK maybe they arent cool with that who knows). I could also go in to the mornings at the NGO and afternoons at the bank (but who wants to show up at noon when people are going to leave at 3pm since its a west coast bank even if you stay later than everyone else)

I mean, I am willing to do the work but 1) How do I construct my schedule so I look like a hard worker as opposed to a slacker who doesnt keep hours. 2) will I be able to go above and beyond still or is this going to limit me to looking like a so-so person.

As far as everything else is considered I told my friends they probably wont see me that much this summer and told my crew coach Im going to take the summer off.