Always Indecisive

That's what I'm thinking, but I think it's my conscience and feeling guilty that's throwing me off. The manager is so nice and I don't want to disappoint her, even though I know that shouldn't be a reason for staying at a job...

Hi, I feel like I'm in a dilemma and am not sure what to do. I am a new nurse who graduated in Dec 2013. My dream was to work in the pediatric hospital I did clinicals at, which is extremely difficult to get an RN job at because of the low turnover rate. I had a past career in pediatrics and love the field much more than adults. I've interviewed for a few positions in the adult field because there weren't any openings at the children's hospital at the time. I was offered a position in a very reputable adult CICU that I accepted last week and won't start until 2/3/14. A day after I accepted I was offered 2 interviews at the Children's hospital on separate units for newly posted positions. I've done one of the interviews already and have the second unit interview on Wednesday. I'm extremely excited for the possibility of working at Children's but would feel incredibly bad if I rescinded the CICU position (if children's were to offer me a job). The manager of the CICU is so nice and sent me a hand-written note welcoming me to the team, and the unit and staff itself are fantastic. I don't want to burn any bridges or lose out on a great CICU opportunity but I also don't want to make the mistake of not accepting a job at Children's since I know how difficult it is to get in there and know that it's where I eventually want to end up. I am supposed to hear back from Children's this week or next week about any possible offers and am thinking that as long as I don't start orientation with the CICU it should be ok to decline the position I've verbally accepted....? I have a horrible time letting people down or with thinking people will be mad/disappointed with me so I'm terrified of making a wrong decision! I wouldn't even know what to say to the CICU if I took Children's... or if I should call the manager herself or just HR? I haven't made any moves yet, so any advice would be much appreciated!!!!