Hi Michy - I did a great class last week which reminded me of your question here. The practice was Hatha vinyassa style with lots of standing variations within the vinyassa - great leg and hip openers (which you need to be able to do the splits). The great thing about vinyassa is that it warms up the muscles so that you can practise poses like the splits safely.
2 poses that I thought might be good to include in your practice were Ardha Chandrasana (crescent moon pose) arms above the head and Ashwa Sanchalanasana (equestrian pose) palms or fingers on the floor by the feet - both excellent for opening the hips and improving flexibility which you'll need to get into the splits.
I find this pose really hard too (I can't fully get into it), so what I do is to place a cushion or blanket underneath the pelvic floor to help avoid strain when I'm in the pose - it really helps.