I can’t think of a video on that topic specifically. As far as preparing your hearts for Mass, I would just try to say a prayer or a few prayers together as a family. You could find one that you like or you could just pray with the kids: “Lord Jesus, prepare our hearts to receive you spiritually in this online Mass…etc…” Then say an Act of Contrition and a Hail Mary and then watch the Mass.
Another thing you could do: I don’t know how many kids you have but you could find a short prayer or write a few yourself and have each child say one themselves, if they are old enough, of course, to do that. That might help them feel that they are playing an active part in it themselves.
Personally, I wouldn’t bother trying to dress the kids up for it. I think, at this point, it’s all we can do just to gather the kids up and get them to focus for a few minutes on the Mass. We can get back to dressing up once the Masses start up again. God understands our difficulties.
Also, I don’t know which online Mass you watch but some are longer than others, maybe you could find a shorter one because let’s face it, it’s harder for the kids to focus when they’re at home and there’s a lot of distractions. One Mass that our family watches often is the one from the Archdiocese of Toronto on YouTube. It’s only about 28 minutes; it has short homilies and the cantors are usually very inspiring in their singing. We don’t bother trying to watch it live or anything; we just watch it when we are able to get everyone ready and focused. Then we offer it in union with all the Masses going on throughout the world at that moment.
Another thing you could do is maybe at breakfast on Sunday mornings before Mass, you could read the Gospel reading and briefly discuss it, again, depending on the age of your kids and their ability to understand stuff. I’ve been watching Bishop Barron’s Sunday homilies and then sharing a few interesting insights with the family on Sundays, sometimes even after we watch our regular Mass. We also say a few prayers each night of the week together. Often, we each state something that we are grateful for. I think that is an important thing for kids to practice doing at a young age.
So just do what you can do and it will be a good thing, a good witness for them.
God Bless, I hope this helps!