Microphones sound best when they are close to the source, otherwise they sound ... far away:)
To get the best sound, I would use a lav mic for each kid and a shotgun mic as a backup, so you have 4 audio channels.
Excellent PowerDeWise Lav mics $34 for a Y pair:
https://www.amazon.com/gp/product/B07CHCSLVC(if you need to connect to XLR, then have to use this $10 adapter Rode VXLR Plus XLR to 3.5mm Female TRS Transforming Adapter
With the Y adapter in the kit, two lav mics get mixed into a single channel.
You still need to mix a 3rd lav mic, so you need a mixer. Better yet, use a recorder with line out which can feed into camera.
Shotgun mic:
https://www.deitymic.com/vmicd3 for $99 or better the Pro version with gain if camera preamp is noisy. This is a high quality mic.
Alternatively, you could use Taskam 70D 4 channel recorder, each lav mic on a separate channel, but connect shotgun into camera.
With Taskam 70D use XLR inputs, not 3.5mm jacks, as they are which are noisier.