I wouldn't worry about it. My daughter goes through stages, I think she's kind of testing her limits and our reactions too. Her latest phase is "I don't like cheese butties". One day she'll eat them, another day she'll peel off the cheese and just eat the bread. I keep offering them to her regardless. She's been through the same phase with cereal, mash, strawberries, yogurts etc.
It's not a bad thing if he doesn't like chips, keep up with the variety, try different foods and see how it goes. I think also keep portions quite small, children can be overwhelmed by too much on their plate, I found that out the hard way!
As for snacking, my daughter has a breakfast, lunch and tea, plus a mid-morning and mid-afternoon snack and sometimes supper. Snacks are things like fruit, breadsticks, yogurt, toast, crumpets etc. Some days she'll eat more than others, it really depends on how well she's feeling, whether she's been really active that day etc. I offer her the same portion sizes each day unless she specifically asks for something, usually when she's been really active and is eating like a horse!