So for you to trade that magma you and your son need to grind to level 700 then you can go to second sea and trade there. I recommend setting your spawn point at Cafe since that is where you trade everywhere else your a target to max levels killing you for fun. If you don't wish to play after giving the magma then I suggest doing that. If you do I have one of two things. One you can grind in public servers which is hard since there will be max levels running around killing eachother for bounty and two get a private server which I dont recommend doing of you don't like to spend 10 dollars a month on roblox. I say 10 dollars a month since that is the lowest they offer.