You won't be able to give the ticket to anyone else according to everything that's being posted and written on various websites. The new tickets have your name on them and if the bioscan fails they can ask for identification. If the name on the ticket doesn't match your id, they can refuse entry.
How many days are you planning on spending in the parks? Why not just get a ticket that expires for your son? I assume you're trying to buy days for a future trip, but lets say you buy the 10 day premium hopper and add the no expiration. That ticket is $401.50 if you order in advance, so you've paid basically $40.15 per day for your admission. But if you buy a 10 day premium hopper with NO expiriation that will run you $295 in advance, a savings of $106.50. OK, now lets say you go in the park for 7 days on your trip. Each of those 7 days cost you $40.15 with the non expiring ticket. Each of the 7 days with the expiring ticket will cost you $42.14 per day ($295/7). So there's only a difference of $2 per day but you've saved $106.50 up front, and you wouldn't have to worry about your son not going again in the future. Just something to consider. If you're not going in for 7 days, you just have to keep working the numbers on the different tickets to see where the breakeven point is for you. I hope that wasn't too confusing.