I might be able to help you - I made a little mobile for my DD loosely based on this and although mine is not as gorgeously colourful (I only had two colours of felt!), it still looks really pretty and DD absolutely loves it. It was a labour of love as cutting out the felt butterflies is quite fiddly, but I felt so proud when it was finished. I am not a born crafter so I think this is a good, simple but attractive project. You could probably get templates for other animals just from a google search.
I didn't have felt beads and was poor so didn't want to order any - instead, I used clear plasticy durable thread for the strands, and used tiny glass beads for the whole thing. Every ten or 15 beads along, I'd add a bigger plastic bead (nabbed from an old necklace I cut up for the purpose). This meant there was no knotting involved - I started with a tiny bead, tied the plastic thread round that, then added a big bead (for decoration at the end of the dangle), then say 10 tiny beads, felt butterfly, fifteen tiny beads, one big plastic bead, 5 little beads, butterfly, etc. My mobile has three strands, hangs from a CD with three holes punched in and covered with felt, and each strand has 5 butterflies interspersed with beads. Not sure I've explained very well!
I do wish I'd had the money to buy all that lovely coloured felt - one day I will do that and make a perfect multicoloured one.
If you do buy felt beads, I think they are polystyrene inside, or otherwise stuffed with something which means they would not slide down the yarn unless you pulled them down yourself (as you do when you're threading them). But I wouldn't imagine knotting the yarn would be too fiddly if you wanted to make it more secure.
In the morning when the light is good I'll take a crappy photo with my phone so you can see what I did. Card should be fine, but do it double-sided so the whole thing is sturdy and doesn't flop. Mine is crap compared to the one on the blog but everyone still loves it Good luck!