Just slide your workbook pages inside page protectors and use a dry erase marker. A rag will wipe it off right away. I left marker on it for several days and a rag no longer worked, but it came off nicely with just a little rubbing alcohol.
I'll just keep a folder of these worksheets and switch them out anytime she gets bored with the ones in her current folder. This also could work for a homeschool consumable workbook that you want to use for more than one child.
Since she now wants to do letters and numbers, here are some more sites for free printables. The last site lets you make a worksheet with whatever words you want. I used it to print out her name for her to trace.