I've no idea who you should have on your new $5 bill but I'm telling you, you should forget about that $ malarkey and go back to £. Not just pounds, though, shillings and pence, too. Twelve pence (written 12d) to the shilling, twenty shillings (20s) to the pound. So much better for your children's mental arithmetic. You go to the shop and buy something for 67c and something for $1.98. What does that come to? Easy, yes? $2.65. How about 13/5 (thirteen shillings and fivpence) and £1 19/10 (one pound, nineteen shillings and ten pence)? Change from spending $2.65 out of $5 is easy. Change from spending £2 13/3 (two pounds, thirteen shillings and thruppence) from £5 is much harder to work out.
Not only that, but the coins are so much more interesting, even without the half and quarter penny ones. You get a 1d (a penny), a 3d (a thruppenny bit), a 6d (a tanner), a 1s (a bob), a 2s (a two bob bit), a 2/6 (half-a-crown or half-a-dollar - from when there were $4 US to the £), a 10/- note (ten bob), and then £1, £5 etc. Even better, things don't just get priced in £, s and d but also in guinneas. What's a guinnea? It's £1 1/- (one pound and a shilling). So you could go into a "posh" shop, like Harrods, and see a carpet priced at 500 guinneas. How much is that? Well, it's £500 and 500s which is another £25 so £525 - I'm convinced it was a way of making things more expensive without them seeming to be.
I hope I've convinced you all that decimal currency is for the birds and stepping 50years (for us in the UK) back in time to pre-decimal currency is the way to go.
