It isn't a wedding, they are shooting a film called 'Ramona and Beezus'
" The adventures of young Ramona Quimby (newcomer Joey King) and her big sister Beezus (Selena Gomez) come to life in this all new film based on the... The adventures of young Ramona Quimby (newcomer Joey King) and her big sister Beezus (Selena Gomez) come to life in this all new film based on the best-selling books (over 30 million...and counting) by Beverly Cleary. Ramona's vivid imagination, boundless energy, and accident-prone antics keep everyone she meets on their toes. But her irrepressible sense of fun, adventure and mischief come in handy when she puts her mind to helping save her family's home." -
http://www.rottentomatoes.com/m/ramona_and_beezus/