Planet Hollywood is not fun for little kids, so I'd just take that one off the table entirely. Rainforest Cafe's are, but they're also found in places outside of Disney. T-Rex would be my choice of the options you gave, but if your kids are really young, I'll offer you the caution that it can actually be a bit scary for some. There's a fake "meteor shower", and the lights change and its loud. My DD was a little turned off by it, and she's basically not afraid of anything (I think it was the noise that bothered her).
Raglan Road has excellent food and good entertainment. Sometimes they invite the kids in the audience up on stage to try out Irish Dancing.
However, if you're willing to travel to a resort and eat there, you'll have so much more/better options for kids. In general, the Disney Springs restaurants are not kid oriented. Ohana would be my choice for a first meal. Point of fact, I'm currently planning a trip which will be my godson's first Disney vacation and I'm vacillating between Ohana and Raglan Road to be his first meal there.