Swapping chainrings on 1x kids bike

[Mububban]

Is it okay to swap chainrings between two same sized kids bike, if one is 1x6 and one is 1x7? I don't want to try and disassemble and swap the entire drivetrain from bike to bike as that's above my skill set, but are cranks compatible between 6 and 7 speed bikes?

LIV AREVA - 7 speed - a Gumtree find for my niece who will only be riding it on general bike paths and doesn't need 36-34 granny gear.
https://www.liv-cycling.com/au/areva-1-20-2015
36 crank
14-34 cassette

HARO FLIGHTLINE - 6 speed - my son's mountain bike that he rides on proper MTB trails and the 40-28 gearing isn't that easy for climbing.
https://haromtb.com/products/flightline-20-2018
40 crank
14-28 cassette

I haven't counted the links on each chain if that's relevant too.

Edited - I said cranks initially, but was thinking front chainrings .

[ironhanglider]

The chainrings will be compatible with the chains if that is the question.

There may be an issue with chain length on both or either bike but the same derailleurs are likely to be also used on 2x or even 3x setups so will have lots of capacity to spare. Iff the chains were a reasonable length to start with they are likely to be ok. I'd be most concerned with the LIV because if it was set up with a chain as short as possible, the bigger ring might make the chain too short which is going to break something. If the Haro was set up with the chain as long as possible, then the smaller ring might make it noisy in the smallest cog but it's not a big issue. It's easier to shorten a chain than lengthen it anyway.

The biggest problem I can see would be if the cranks were designed to use different length BB axles. That could cause significant issues, like the chainrings fouling the chain stays or tyre if the crank sits too far inboard, or chain drop issues if it is too far outboard.

Is it possible to swap just the chainrings?

Cheers,

Cameron

[Mububban]

The chainrings will be compatible with the chains if that is the question.

Is it possible to swap just the chainrings?

Yeah that's what I was thinking, but for some reason I typed crank rather than chainrings . I've edited the topic for clarity.

[ironhanglider]

If they are both removable, then make sure the bolts are the same distance apart before you start. After that just give it a go.

Cheers,

Cameron