If he has to cancel you can just call Disney and have them change the amount of adults on the reservation from 2 to 1 thus dropping his tickets and free dining from your package. You will most likely need to pay a $50 change fee because any changes that lower your package price less than 30 days before arrival are subject to that fee. You can also edit all of your dining reservations (assuming you have TS ADRs) from 5 people to 4. This can be done online or over the phone with no penalty.
Edit- If you decide to not change the number of people and keep his unused tickets for a future trip, remember that if you book another package in the future you will have to get tickets for everyone in the party, in which case you'd end up with yet another extra set of tickets. You'd have to book a room only reservation and then get tickets separately, meaning you couldn't get the dining plan (free or paid) or package discounts. Just something to think about.
Just want to point out two things. If your DH ends up not going, you DO NOT have to touch your ADR's. If you can get a reservation for 4 instead of 5, great. If you can't, leave them as they are. There is no penalty for showing up with 4 for a reservation for 5.
Also, if you end up keeping your DH on the reservation even if he doesn't go, that does NOT exclude you from booking a package with dining in the future. Yes, with dining PROMOS you will most likely have to add tickets in order to get free or reduced dining, however it does not EXCLUDE you from adding dining to a room-only reservation. If you end up with an extra set of tickets, you can always book a "ticketless package" with just room and dining (you can even do this with a room-only promo) and then purchase any tickets you need separately.
You have a few options:
1) Keep things as they are and if your DH can't go, simply keep him on the reservation. As a PP pointed out, you can then use his extra dining credits and save his tickets for another trip. Those tickets will remain in your
MDE account and can actually even be transferred to another person in your account for a future trip as long as they aren't activated. If you think you will go on a future trip and those tickets will be used and if you think you will get value out of those extra free dining credits for you and your children, this could be the way to go.
2) Drop him from the reservation if he can't go. As PP pointed out, you may be charged a $50 change fee if this is done within 30 days of check-in. His tickets and free dining credits will then be taken off the reservation. Make double sure when you are on the phone doing this that they maintain your free dining promo when making the change.
Only you can decide what's more beneficial to you, paying the $50 change fee or paying for the tickets and keeping his extra dining credits.
