How much alcohol for 40-50 people?

That should be more than enough if you are staying away from liquor totally. 1 half keg should do the trick for 50 people (I've had house parties with 75-100 and not gone through a whole 1/2 keg, but there was liquor there too)

I think 2 kegs is more than enough!! You may have too much, but it is better to have too much than to little

Hmmmm......what to do what to do. lol I was thinking 2 halfs so we can have a Mexican beer and a regular light. Maybe that's too much?

Variety is never a bad thing!

If you have too much you have too much, it's not the worst thing. What would be bad is if you ran out! I am supplying all of the liquor for my wedding and we are buying a lot of excess knowing that we can either return it or just use it to stock our home bar, which is the only problem with kegs, you can't get away with that, but still better to have more than to run out!

True!

Get a pony keg or two. They are pretty small, but you could get a variety. Here, they are smaller than a half so maybe even 3. It's a quarter size and holds 63 pints or 7.75 gallons.

You can try using an online wedding alcohol calculator. This one will tell you how much to buy and how much it will cost:

The Wedding Alcohol Calculator