I'll bet they;re learning these wonderful habits at daycare, which means you're going to have a challenge on your hands establishing some rules of behavior. If they eat 2 of their three meals away from you, it's going to be pretty tough for you to get them to behave otherwise.
One thing you can do is ask your provider what he/she's doing at mealtime to encourage good eating habits, and put some burden on them to "teach" them to not throw food, use utincels etc. Ii even go as far as to say since the kids have been with them they've developed these bad habits, and you'd really like them to work on this with the kids.
Then at home, I'd do time outs if food starts flying. If treats or desserts are custom at home, I'd threaten taking that away from them.
Lastly, I'd reward good behavior at the table. Encourage them to actually change their clothes or tidy their clothes before meals, and teach them how to set the table properly. Find an etiquette book for young children and read it to them, and explain that meal time will now be special. It will now be as important as going to a tea party or grandmas...etc.
Enforce a good voice level, no talking with food in mouth, how to use a fork and knife (toddler versions do exist) and napkins on the lap too. If you make meal time a fun but special event every night, they will develop a reverence for it..and hopefully the food will stop flying.
Girls really go for this...but the guys will too if you get them in on helping with meal prep, serving and setting the table.
Make it a family affair...and remember, they're never too young to start learning good manners.