Your seats are excellent, yellow r section 11 rows back. Looks to be 100 yards short of the finish line. Should be shaded all day.
https://www.eseats.com/sports_ticket...nt_stakes.html
We attended the Big Brown Belmont and I'd also strongly suggest the LIRR as opposed to driving in but your departure station will depend on where you're staying. We stayed near JFK airport and took a train out of Jamaica.
http://web.mta.info/lirr/getaways/belmontpark/index.htm
Personally I'd stay in the seats and just pick him up to your eyelevel. Follow the crowd in front of you and if they stand on their seats than you do.
Should AP win the Preakness the crowds will be huge but the place is so big the crowd is manageable especially if you don't have to visit the women's rest room.
Some of the local New Yorkers can help further with the LIRR if you post where you'll be staying.
You and your kid will have a blast regardless, but if AP wins the triple crown it'll be something you and he will talk about and remember forever.