Sending shoes from the outside directly to an inmate is rarely permitted. Most facilities, particularly federal prisons, do not allow personal footwear to be mailed or brought in by family. The security and contraband concerns around outside packages are tight, and shoes are rarely on the approved items list.
The good news is that size 17 is carriable through the federal commissary system. The Bureau of Prisons commissary stocks larger sizes specifically because the inmate population includes people who cannot be accommodated by standard sizing. Your inmate will not be walking around in shoes that do not fit.
Here is how it works in federal facilities. The prison will issue one pair of work boots at no cost, with the cost covered by the institution. Those are for everyday movement around the facility, work details, and programming. Sneakers are a separate matter and are considered a commissary item, meaning the inmate pays for them out of their account. Expect to budget roughly $50 per pair, though pricing can vary by facility and by which brands the commissary carries at any given time.
The extra wide width may limit options depending on what the specific commissary stocks, but the case manager or counselor at the facility can tell you what is available in that size and whether a special order is possible through the commissary system. Putting money on your inmate's account so they can make that purchase themselves is the most reliable path forward.