I'd probably schedule some set days to see them - so that they had at least one day minimum a week to see me _if that is what they wanted to do_ too. If I was dating two people who didn't live with me but wanted to see me lots, I'd probably set two aside for each a week, then if one was busy that week, I'd see friends or do laundry or see my other partner (but that's just what would work for me).
That would also help if they start dating other people, to know that they always schedule around those date nights with you, so there's not a lot of confusion about schedules or you end up not getting to see them sometimes because you only had Friday free and they made other plans that night because they didn't know.
Really there are benefits to many different types of scheduling, it really depends on the personalities of those involved and how you can compromise to try to get everyone's needs met. Some people WILL not like making or sticking to a schedule, some people can't do without, so I'd talk to both my partners before thinking about it too much.
Happiness will never come to those who fail to appreciate what they already have.