DS2 is 3.7 years old and has always been a bit of a rubbish sleeper. He still wakes up several times a night crying and shouting and won't go back to sleep until you go into his room and lead him back to bed. He has a gate on his room (mainly to stop him falling down stairs in the night cos we can't fit one at top of stairs) and he stands at it shouting and rattling the gate until someone goes to him. If you ignore he just goes on and on and I always cave and go to him as am worried he will wake up DS1 aged 6. Then after a night of waking us up three or four times he is usually awake proper by 5.45am. He has a gro clock and knows he is supposed to play quietly in his room till the sun comes up at 7 (like his brother does) but he rarely does. This morning he turned it off at the wall and pulled his gate down 
. We have tried reward chart / bribes / punishment etc but it never works beyond a few days.
Just looking for solidarity - really feel by now that he should sleep through and entertain himself in the morning till I go in but it just feels like it's never going to happen. DS1 never did this, he always just obeyed his gro clock!
DH and I are going away for two nights next weekend for our anniversary and it will be the first time we have had a night away without kids since DS2 was born. My sister and brother in law have kindly offered to come and stay and look after the boys for us which is super generous but I'm worried he is going to be a nightmare for them! Their kids are grown up now so they're not used to small people waking them up all night.
Any advice on when I can expect my child to sleep through or at least not wake the whole household up every time he wakes? Thanks