new event

i have been a 100, 200, 400 runner since 7th grade. i am currently a freshman in high school. my season bests so far this year are 11.82, 24.64, and 55.71. my coaches say i run the 400 much more relaxed and aggressive than my other events. they want me to try the 800. i ran one 800 in 7th grade and ran a 2:26. I am currently 4" taller and weight 25 more lbs than i did at that age, and am far stronger. do you think this is a good idea? if so, what kind of times should i expect? i know i am kinda short on details but i would just like a generel consensus.