How can I encourage my 8-week-old twins to eat baby food?

I have a 2-year-old girl and 8-week-old twins. All three girls now love each other and would not want to be segregated. My 2 year old is thrilled to have playmates, and the babies really enjoy being groomed, licked, and loved by their older sister. They spend the days (while my boyfriend and I are at work) running around and play-fighting each other, and I would really hate to have to keep them completely separated.

I set out three food dishes everyday, and the babies always go for the adult food first. Is this a big problem? What can I do to change this? I just want everyone to be eating the proper food, but it seems impossible to control.