Wrt putting you twins down awake, this is most definitely a good thing if you can do it, as they will learn the art of self settling & if they wake in the night will be better able to put themselves back to sleep. I think your early waking problems are more of a routine issue though, than being related to this.
I'd say the reason you might be getting early waking is twofold. Firstly that nap at tea-time is pretty long at 1-1.5hrs. Around 6-7 months is when most babies drop this tea time nap & just have a morning & an afternoon nap. Taking a long nap so close to bedtime is likely to cut into their night sleep. Secondly, they are taking a long and early morning nap. Of course they need it at the moment, because they are waking early, but this will keep you in the early waking cycle, because they are able to catch up on the sleep they missed at night with the long morning nap. I would address this as follows:
firstly, cap the tea time nap to 45mins max. You might need to bring bedtime a wee bit earlier to 7/7.30pm to compensate for the shorter nap. Hopefully they may sleep a bit longer at night. Even if they continue to wake up at 4am they will be getting a longer night's sleep because of the early bedtime.
Give this a few days to a week to take effect & then very gradually start to shift that morning nap later by just 5mins every 3 days. You do this slowly so they don't get too overtired. I would suggest pushing the start time of the nap to 9am. At this stage they are still so young that I wouldn't cap the nap unless it goes over 1.5hrs, as you need them to still take a decent length afternoon nap.
As the morning nap gets later, the lunchtime nap will also gradually shift later & so will the tea-time nap. You will find you need to trim the tea-time nap down to nearer to 30mins or they won't be ready for bed at bedtime.
So ultimately, you are moving your morning & afternoon naps a bit later, with the ultimate aim of cutting back the tea time nap so short it can eventually be dropped. This will most definitely help your early waking issues.
HTH.xx