My kid is driving me nuts...in the best way possible

All my son wants to do is eat. Except at meal times. We get home from work/daycare and the first words out of his mouth are what kind of snack he wants. Depending on what he wants and what we have, I try to accomodate him. I try to encourage healthy snacking and offer fruit when we have it or maybe some popcorn. He'll eat what I give him and then come back 5-10 minutes later asking for another snack. This repeats all afternoon long. I'll be in the kitchen preparing dinner and he comes in asking for a snack. I allow one snack after school, maybe 2 depending on what the first snack was. I know from experience that if I give him more than that, he's definitely not eating dinner. Anyway, even with one snack, half the time he doesn't want to eat. I don't know if he's just being difficult (he's 2.5), if he doesn't like what I prepared, or if the snack filled him up too much. Since I've been typing this post, he's already asked me for Shrek cereal, Lion King cereal, poptarts and Nutty Bars. He's eaten one of those prepackaged tubs of jello and half a nutty bar already. At school I know that he has breakfast, a mid-morning snack, lunch, and an afternoon snack. I want to make sure that he's not hungry, but I'd rather have him eat the nutritious meal I prepare at dinner instead of snacking all afternoon. Should I let him snack, and buy more substantial things for him to snack on, or do I say no to snacking and wait until we eat dinner?