Need Help with Pack Introductions

So, my boyfriend and I have become quite serious. We are making plans for our future together (which is very exciting to me!), but he has two rottweilers (a male who is about 3-4 years old and a female who is 2) and I have two miniature dachshunds (two females – one is 9 and one is 7). We are uneducated on how to integrate the two households. We tried meeting at the park to introduce them, but that didn’t go so well. My girls barked at the big dogs the whole time and the female rott tried lunging at the little ones. We have to make this work so the two of us can move forward. Any ideas on how to do this safely and effectively?

Thank you,
Stace