When my husband turned 50, it just so happened that his father turned 80 (their birthdays are a month apart). My MIL and I had a combined birthday party for them and invited all the relatives. It was a sit down dinner and a lot of fun. Both my husband and his father had a great time talking to relatives they hadn't seen in awhile. It was not a surprise party.
One thing you can do is a collage or scrapbook of pictures for your husband - from birth to present day. My husband loves craft beer, so he received 50 bottles of different craft beers from his cousin, who is also a craft beer lover. My husband received gift cards in $50 denominations.
Hope this helps!