How to have a succesfull small wedding?

As long as there's food and open or cash bar, don't worry about people being bored. If you have no alcohol, that will cut some time off your reception, also if you don't serve a full meal that will cut it short too. But if you're having a cocktail hour, full dinner service plus dessert, that will take at least 2.5-3 hours, plus your guests probably want to see you do a spotlight dance with the groom, cut the cake etc and that all takes up time and keeps them entertained.