Damkina

I have recently purchased the Lazy Girl Claire bag pattern with the intention of adding a Mermaid appliqué, fabric paint and beadwork to the middle panel on one side, instead of the pockets on both.

What I'm unsure of is, should I still use iron on batting as suggested in the pattern, or the usual sew-in/on as for quilts as I don't want to wreck the finished beading with too hot an iron?

Also, I have the stamp (SeaSallie) i'll be working from and fabric, paint, beads etc, but wondered if anyone knew what permanent ink stamp from the UK that I could use that would stay on fabric, and yet be washable?

Thanks in advance for any help
Joanne