Your family is lucky to have someone as caring for them as you -and they will care for you right back. It will be just fine if you explain it's about health not weight I'm sure. Let them know about non-scale victories like about how much better you feel and other activities you can do now. They will be proud of you for being stronger and healthier. Remind them about well-balanced nutrition and how maybe you haven't been balancing things right lately and need to eat some different foods to balance out your meals.
Also, I have an alternative that might help with the ice cream bit. I get no-sugar fudgesicles. (They also make popsicles and creamsicles) These might be more helpful in that 1) they're cheaper so you can afford them for the kids too, and 2) I always avoided things as a kid that pronounced they had no sugar added. It's like buying ice cream in a spinach box.
I think the fudgesicles are very satisfying and they are only 40 cal/bar. (See them here:
Popsicle Healthy Options Both Krogers and Wal-mart carry them where I live. Might be an option for you, it's really helped me.
As for the actual meals, I think it would depend on the meal. Serving size is definately a consideration no matter what you fix, but maybe you can find small ways to change your portions, like not adding cheese toppings etc. In my family someone was always picky about eating something, so it wasn't a big deal if 1 person ate differently than others. If you can alter the meal, but if it's just not practical just make a chicken breast for yourself instead of a burger, or whatever, and just say you felt like eating chicken instead. I think you can make dinner differences without disrupting others. I definately agree that you should make enoughy healthy options so that the kids can choose them too. For example, if you make a side of mac and cheese and a side of salad, you can eat the salad and the kids can have either or both. You don't have to eat some of everything you cook.