ok firstly, i really don't know anyone who gives a crap about the law when it comes to sex - no-one.
The police have got more 2 worry about.
next, you're best friends right, so there's gotta be a lot of trust there. you're both going through puberty now and you won't again so this is the only decent reason (except university / college) to experiment - you might look back when you're older and think "I wish i was a bit more open minded."
if you're nervous, just start off lightly. maybe just masterbate together. even us straight guys do that sometimes. if you feel more comfortable, move on to something more - but if it feels wrong - stop.