My family is celebrating a major event this summer in the US. There will be 16 adults. Most are not regular alcohol drinkers and do not have adventurous palates. Thus, I think a champagne that's not too dry but slightly sweet (without being too sweet or sugary) would work well for them. Our champagne budget is limited.

Here's what the restaurant where the dinner will be held offers in this price range:
Cooks Brut
Korbel Brut
Chandon Brut
Piper Heidsieck Brut
Gionelli Asti
Martini & Rossi Asti

My preference would be to bring 3 bottles from a small producer in France, but the restaurant charges a $20/bottle corkage fee so I'm wondering if it's worth it if indeed any of the above choices are acceptable.

Opinions, please?