Advice - Nontarget with a 3.3-3.5GPA

So I go to a nontarget and have a mediocre gpa 3.3-3.5. Luckily, I landed an internship at a boutique through grinding it out cold calling/emailing alums and any sort of ib establishment in the area. This boutique is very small and all of the members have remarkable experience in the industry and im assuming contacts as well. Im not given as much responsibility as lets say a BB SA because they simply dont have the resources to trrain me, but i have been getting exposure to modeling, and their current deals etc. Question is I have an interview with a fortune 500 for finance/acctg internship this summer that feeds into their 3 year rotational program. I want IB, but am concerned whether I should pass this f500 opportunity up as it is my safety net. What should I do.....Will my gpa really hurt if my current internship gets my interviews through connections? They have tons of experience from being ex partners at MM companies to ex VPS at top tier BB's etc.