First off...sorry to hear about grandpa.
The first thing you need to do is take HALF and put it away...kids college funds, stocks/bonds, a high yield savings account.
If you keep it all handy, you'll spend it before you know it. By putting away half (you're still gonna be left with aprox. $225,000), you know that stuff is packed away for a rainy day. If that rainy day never comes, then you know you'll have enough for other things.
Take the remaining $225,000 and invest it in things that'll show a return. If you own your home, do those repairs you've always wanted to do...raise your home value. Take your wife and kids on a once in a lifetime vacation. Buy your wife the one thing she's always wanted, but you've never been able to afford.
Then, worry about this hobby. It takes up enough of our money as it is. Get the good things in life out of the way first and then splurge a little on that one fish you've always wanted or that dream tank you've been day dreaming about.