My twinnines will be 1 in just 2 short months. I rented a pavilion at the beach. Between family and close friends, I'm expecting about 50 guests. We will have BBQ, there is a great playground right next to the pavilion (for young and older kids), and ofcourse the beach itself. I will probably buy just one main cake and just get 2 "smush" cakes - its a little personal cake for the baby, so I'll just get 2 of those.
As long as DC dont mind, I will keep having 1 party for both. Once they decide that they want separate parties, I'll do that. Also, once they are old enough to understand and actually enjoy their party, I will probably have a separate party for them with their friends and a separate one with family.