What a great goal and plan to reward yourself!!
For me, part of the fun of traveling is trying foods that are local to the area I'm visiting. That can be challenging while you're being weight-conscious, but it is possible. Most vacation destinations have restaurants with menus online, so you can plan your meals. Splurging can be about calories AND cash, so it really helps to plan when and what to eat out and what to keep consistent. But buying and taking food ahead of time isn't really a cost savings over buying food at your destination - especially if you're paying to check a bag. And, most places will have your standard groceries and health food shops, so that you can pick up any kind of meal replacement you use once you get there.
I never check bags, just too uptight I guess, when I travel.
A carryon and a good sized duffle/bag work well for me if my trips are in the range of 5 days.
It does make sense to take a meal and snacks with you for the travel portion of your trip, though you do need to make sure you meet TSA guidelines. Also, I *always* take a stainless steel water bottle with me - if you take it empty you can go through security without a problem. Then I buy a couple of gallons of water at a convenience store or whatever's near my hotel and keep them in the in-room fridge (or just get ice, if there's no fridge in the room). That way I'm sure to drink a lot of water, but not spend a ton of money on bottled water (not to mention all the plastic waste).