I wouldn't turn myself in and admit to ANYTHING just to get off my friends who were watching my grow. For all you know they did something dumb that made the cops bust them. Also, as you say, perhaps you and they will BOTH be charged anyway, no matter what you say. Ask an attorney how to handle it.

It is fine to ask for an attorney for a referral to a criminal attorney who handles drug TRIALS (some attorneys may mainly plea bargain, and don't have much experience with trails). When you meet with your attorney, ask SPECIFICALLY how many similar cases (pot and pot growing) he has handled, how many went to trial, and how many he was WON. He has to tell you the truth so you CAN take his word (and he WILL know the numbers, so don't be shy asking). He can also advise you whether to plea bargain, or go to trail.

I can only speak about laws in the USA.

There will most likely be a warrant out for your arrest. Your attorney can find this out without YOU having to yourself. Usually you have to go to the police station and fill-out a form (and pay a few dollars) to see if you have any outstanding warrants. So, you really can't do that safely yourself.

If you can't afford an attorney to defend you all the way through plea bargaining or trial, after you turn yourself in (if that's what your attorney recommends) you will be assigned a public defender. These attorneys are sometimes fine, but it is of course better to have hired one of your choosing.

Your bond will be 10% the bail, so make sure your attorney (or someone trustworthy) can handle bailing you out, perhaps the same day you turn yourself in and are "booked" (finger printed, mug-shot and locked up in the local jail). A bail bondsman can handle that stuff, too (perhaps for less money than paying your attorney). A bail bondsman will accept security to cover the bond (such as anything of value, I suppose).

Do look up the statutes in your state that have to do with possession and growing. NORMAL has a brief run-down of them, but you might as well bone-up on what is on your state's laws, if those are the ones you'd be concerned with in the Netherlands. It's good to know the laws (statutes) as well as (or better) than your attorney.