As of Deathly Hallows, Hagrid would have been about 68 years old.
In Chamber of Secrets, it is stated that Hagrid was in his third year (about 13 years old) fifty years ago. Which would make him 63 during Harry's 2nd year.
Voldemort would have been a few years older than Hagrid, meaning that he died in his early seventies.

Hagrid being older than McGonagall just doesn't seem right to me.

_________________
"Just one more, Master Harry, for luck?"

Alas it's true. I found it hard to believe that Hagrid was older than McGonagall as well, so I went some researching. According to Harry Potter Wiki, Hagrid was born on December 6th, 1928 and McGonagall was born October 4th, 1935.

_________________
It is our choices, Harry, that show who we truly are far more than our abilities. -Dumbledore <3
Pottermore: GoldQuill28467

We know wizards live longer than Muggles (hence Dumbledore being well over 100 when he died), so certain people seeming younger than they really are should not be uncommon; it's the stage of their overall life they are in.

What about Harry's kids? We know Teddy is 19 at the time of the epilouge; I would guess Victoire is 17, as James Sirius says Teddy has "come to see her off". Al, of course, is 11, as is Rose; and Lily Luna (and I think Hugo, too) is 9. I think James Sirius is about 13, that just seems like the right age (plus, it makes it two years in between each new Potter kid!) But what about Molly and Arthur's other grandchildren, Victoire's brothers (One of them is Louis and I forgot the other!), Molly and Lucy, Roxanne and Fred (that would be Bill, Percy, and George's kids, in order!)

_________________
"You said to us once before," said Hermione quietly, "that there was time to turn back if we wanted to. We've had time, haven't we?"
Pottermore: SeekerSpell89, DawnDream24997
Wand: Cedar/Cypress, Pheonix, 10 3/4 in, Slightly Springy