You have to just do what suits your DCs IMO.
I have:
3yo - goes between 8.30pm and 10pm to wake at 7am
1yo - goes between 8.30pm and 10pm, but sleeps for up to 1.5 hrs at lunchime.
Both the little buggers are in beds in our bedroom! DS (3) has the "marital" big bed all for himself , sometimes DH is in there with him and DD (1) is in a single bed with the cot used as a bedguard. TBH, it's the only thing the cot has ever been useful for - neither of them would sleep in it and I have no idea why. It is a nice cot!
Anyway, I lay in bed with each of them until they are asleep/drowsy enough not to mind me leaving.
I don't recommend taking any sleeping advice from me .
I am absolutely at some of your 3yos going at 7-7.15.