This 'About.com' page has some suggestions, but I don't know how to evaluate them.

I'd also like to know how to say, "May God grant you many years."

From book Latin for All Occasions by Henry Beard.

Tibi diem natalem felicem!

For your second question, I'm going to take a common Italian toast and see if I can put it in Latin. It's just a guess...

Vos Deus tribuo centum annus!

God grant you 100 years!

I think a standard "shorthand" method, used often for priestly ordination anniversaries, is
Ad multos
or
Ad multos annos


Edward Pothier

in a monastery, a monk's feastday is announced at dinner (at the refectory) thus:

Pax! Cras recurrit dies onomastica reverendi patris Pauli. (the community responds: Deo gratias)



similarly, in lay terms we could say:

Hodie recurrit dies natalis Gaii Jacobi Smith. Ad multos annos, vere!