Don't feel bad about the whole swimming thing and waiting for the people of your age to leave. You should be proud of going period! I don't even go at all! So be proud of yourself that you're going, and eventually you won't care about what others think and go in whenever!
However, having said that, you should also realize that you've lost a lot of weight and you look completely different than you used to. Try not to see yourself like that anymore and have confidence in how awesome you look now! So to hell with anyone else being there, just go in and be proud of everything you've done and accomplished.
Just also want to note on the calorie thing again! It's still far too low. You need a bigger breakfast too, 100 cals is a snack not a meal!