Dh is dreading this, what with fil hooking up with randy 44 year old who was a virgin until they met.
Mind you his dad is 61.
Just as a slight downer, my friend had this recently and she made a real fuss and then her Mum lost the baby and she felt awful, maybe leave it until after 12 weeks to get too excited at her age?
Now for the up stuff: wow! Your kids will LOVE the novelty of an aunt or uncle younger than them- my friend at school had one and it made her seem way cool. You can also get mucho satisfaction looking on and saying ' you know, these day we don't do it like that....' 
Good uck to her!