This is an excellent opportunity for da`wah (inviting others to Islam). That doesn’t mean that you have to preach to the guests, but it does give them a chance to see a Muslim family “at work” and to see that Muslims are really not so strange, after all.
As a parent, you should be glad that your child has non-Muslim friends because it means that he or she is not totally isolated in school (if there aren’t many other Muslims). It also is a sign that your child is not ashamed of being Muslim, not ashamed of telling the non-Muslim friends that he or she is fasting, not ashamed of the family. And if your child wants to invite the friends home, it is a sign that the child has chosen friends that he or she thinks you will not be upset with. This is all to the good.
Having the classmates over for iftar gives you a chance to see what kind of friends your child is choosing in school. Talk with your child’s guests and ask them about their interests and families in a friendly way.
If you’re in a country where Muslims are a minority, it is important that you and your children learn how to deal with non-Muslims. There is nothing wrong with socializing with non-Muslims as long as you don’t break the rules of Islam such as by having free mixing of the sexes or drinking alcohol.
Enjoy your iftar with your child’s classmates. And if you don’t have extended family nearby that you will be visiting on `Eid, maybe your child would like to invite these friends or others for an `Eid celebration. At least let your child take some cookies to school or friends after `Eid to share the happiness of the season with others.