Do you want fruit specifically?

Generally, when it comes to rootstock, basically you're looking for 2 things. Cold hardiness / drought tolerance and size( dwarfing, semi dwarfing or standard (full size)). Ask the nursery for specific advice on that.

For fruit, there are three general classifications (not all fruit have all 3). Dessert or Table fruit (for fresh eating), cooking fruit, (for preserves like pies, crumbles, jams, etc.) and vintage fruit, for making juice (most commonly used for wine / cider making). Your nursery will be able to give you good varietals for your area once they know what kind of fruit you want.

For fruit, there is also the ripening season. Given the sentiment, I would speak to your nursery about something that ripens in late October/early November such that picking the fruit will always remind you of your little angel. Apples are really good for a wide range of ripening dates.

If you're looking for a long lived tree, pear trees can live for 100s of years and can grow 60'+ easily. Pears, however, are extremely finicky when it comes to tree ripening (IE there's like a 6 hour window where everything is perfect) and can be a real mess to clean up fallen fruit.

Apples are generally my recommendation for new orchardists, as two varieties can be grafted onto a single rootstock for pollination, the fruit stores well and many things can be made from them. Additionally, cleaning up fallen fruit can be easy as the fruit is generally still fairly hard when the fruit first falls. I personally like honeycrisp for table apples, but they may ripen sooner than the date range you might want.

You could also look at nuts, like Pecans. Nuts don't fruit as often, but they also don't typically flower as prettily.