You said you upgraded from free dining. Is this an upgrade from the Counter Service dining plan (staying at a value resort) or the regular dining plan?
We personally love the park hopping, and always do add it. It's a personal choice, but we think it's worth it.
Which hotels are you staying at?
Also, with such young kids, Sea World added sounds like a lot to me. Unless you got the free military tickets, but that is just my opinion.
If it's this year, also register for the birthday promotion. We did that in March for my DD's birthday. Sign up online, then bring a copy of her birth certificate. Since you already have tickets (they will make you prove that) she can get a Disney gift card valued at a one day ticket! They also offer some stuff like a fast pass, but really the gift card is the best deal. My daughter had so much fun shopping for cute stuffed animals with that thing!
Have a great trip!
PS: Do you have your dining reservations? I don't know your dates, but that is important! Coral Reef can be hard to get into, and I have heard CRT is very hard. We loved the new Tusker House at DAK, haven't tried the new Yak and Yeti, but DS doesn't like Chinese food. Also, if you decide to do a park the first night, it's not much to add a day to your tickets if you've already got 5 day tickets.