Which snack packs do they give him? Personally, I am against packaged foods for baby that young. It's one thing if it's gerber or equivalent packages/jars of fruit or veggies, it's totally different if it's something else. I would read the back of the pack to see if there's any potentially harmful substances in those packs (i.e. dyes, sugar, large amounts of sodium, etc.). plus at that age, you're trying to teach your baby how to eat real food, so it's not a good idea to just give up on feeding the "good food" and take the easy way out because in the long run, you are creating a picky eater. i know it's easier to just give the baby something sweet, but you also need to feed other stuff too (for both nutritional and educational purposes).
i would try tasting the food they're trying to feed him and if it's too bland, add some herbs to it (you can't use salt & pepper, but you can use basil, rosemary, thyme, oregano, dill, etc.) that might make him like the food better. and just try different combinations of veggies/fruits so see what works. what i also found was that sometimes, if my son (who is 7 months old) is not really hungry, he won't eat certain foods (but would still eat a teething biscuit), so rather than force-feeding him or opting out for milk+cereal or cookie, i just wait another 20-30 minutes & try feeding him again & for the most part he eats everything with no problems. Good luck to you!
i just read the responses below & would like to add that i disagree with moms saying that grandparents know what they're doing. yeah they raised you, however once they become grandparents, somehow things change & they want to spoil the kid rather than educate them. spoiling is good in moderation, but not through giving the baby foods that are not great for him. they'll have plenty of years to feed him sweets, chips, pudding, jello, etc. for now, a jar of unsweetened apple/pear sauce or a banana can be just as much of a treat as jello/pudding. i would also keep in mind that the chemical composition of some of these 'snacks' has changed since you were little and they now contain preservatives, sugar substitutes (and if you remember from pregnancy, most of them are harmful for the baby), hydrogenated oils, stabilizers, etc. which were not used (or at least not in these amounts) 20-30 years ago. and i'm sorry to say, but at this point, chocolate is less harmful to the baby than some of these "healthy snacks" or "fruit candy". so again, i would read the back of the package very carefully and stock up on baby-friendly snacks so that grandparents can have them easily accessible.