I sent 4 shoebox sized packages during PS, mailed one about every 1.5 weeks. The first box was mailed a day before I-day, and it was a plastic box with a tight -fitting lid, stuffed with high-protein bars, sports drink water flavor enhancers, trail mix, healthy snacks. (Bancroft has mice and mids need at least one-mouse-proof container. for snacks.) No candy, sugary stuff, or junk food- it will get confiscated by the detailers. The other boxes contained extra bottles of shampoo, body wash, foot powder, and more snacks; postcards/cards; inspirational sayings that I found from a "famous quotations" book and handwrote onto colorful index cards, gel inserts for running shoes. I also sent a desk-top sized 4x6 in. American flag and a stand. (They will need the flag to avoid being accused of mutiny if more than 2 plebes are in the same room at the same time-wait until after I-day to send it.) Take the protein bars and drink flavors out of their original boxes and you can fit more to mail.
Last year, plebes were REQUIRED to write a letter home to parents within the first week of PS. (Mine was so exhausted he forgot to turn it in by the deadline to be mailed-I didn't get it until he gave it to me at PPW.)
Do not under any circumstances, send cutesy stuffed animals to female plebes. It's not college.