I offered to babysit a 4 yr old and a 5 week old but...?

give it more time, dont quit and leave her out in the cold because of one bad day. babies are fussy, they have bad days to, and they are all different, what worked for your babies might not work for hers, ask her for advice on what works best to calm her baby. as for the 4 year old, instead of popping in a computer game to keep him from annoying you, why not keep him happy and stimulate his brain by playing with him, do something similar to what he wanted to do. he wanted to watch spiderman, but he couldnt do that, so instead suggest that he acts out spiderman with you instead, or you can look up spiderman episodes or the whole movie on youtube. just give it more time.