I think it’s a great idea. I have a 7 year old too (also a 5 year old) and would love to get them something like the F24 or F24x for longer rides. I just bought a Felt a couple of months ago, love it! In the shop they had an F24x on the floor. My son, the 7 year old, isn’t big enough yet for it for sure. He’s certainly one of the smaller kids in his class, I think 47 inches tall, but the size ranges on Felt’s site for the F24 go down to 4’ 5", and just from my eyeballs it seemed about right. So if your daughter is getting close to that height it might work, otherwise I think it’s just going to be a little big. Of course, she will grow into it.
I started doing long rides, ~50 mile days, at about age 11 and loved it, so I’m definitely going to try to get my kids into it, but I think they’ll be 9-10 before they fit the F24. But I’m 5’ 5", my wife is being generous when she says she’s 5’ 0", so maybe your kids will be quicker to fit the bike.