I don't know what it is about hot dogs that make them a kid-magnet, but your toddler is right in there with many other American children. Unfortunately, in addition to being very high in salt and fat they are full of nitrates, which are linked to certain types of cancers. Nitrates are preservatives added to enhance the look of the meat, keeping hot dogs nice and pink.
Actually, cold cuts like bologna, pepperoni and sandwich sausages also fall into this category, but all is not lost. In the past few years, lean, turkey-based hot dogs have become plentiful and affordable. These are much lower in offensive additives, but always read your labels before buying. You can often avoid extra additives by buying from the deli instead of prepackaged items. The deli workers will be happy to review the label with you.
By the way, your mother-in-law is correct about children choking on hot dogs. Even children who cannot chew other meats can bite off large enough chunks of hot dog meat that can lodge in the throat. And even infant-sized franks are not recommended because they can cause choking. Hot dogs are best left to when a child's first molars have erupted.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.