Introducing 2 3I Broodmates to my 4i P Imp in a 10g?

Currently my 4i is in a 5g, and the two 3i's should be at my door tomorrow (weds), the two 3i's are broodmates and are near a molt.

I will be putting all three of them into a new 10g, that is currently housing my Cavi (dont worry I am moving him into a 5g lol).

I know the only one I need to worry about is the 4i I have right now cause he will be a 'stranger' to the two broodmates.

Will the larger size of the 4i be a factor in introducing the three into the 10g? Since its just 1 instar difference? I wont have to rearrange anything in the 10g since it is all new to the 3 of them. I will also be diggings starter burrows for them as well, it already has a lot of potential hiding places (under logs and pothos leaves).

I will make sure to feed all three before throwing them into together.

Any other tips to introduce them?

I don't see much problems in it. I never witnessed cannibalism, even in solitary species.

Do I have to seperate them during molts?

Nope, just leave them alone as much as you can, makes for happy bugs!

Yeah I know that, a friend told me to put the 3 of them in a large container just so they get a feel for each other before putting them into my elaborate 10g

I' d say that would make it an extra step and would stress them out that one extra bit.
Put them together and be ready to separate them for the first few minutes....

After that, most likely no accidents will happen when they are well fed and have enough room and hides. Get along, or get eaten.

They have no social bonds like more complex creatures do.
No real brain, no real memory.