I just took over as our PTO president, too. It is overwhelming planning for Santa's workshop, but here's what we did:
All items are $1 to enable all childrent to participate. Each child is limited to 10 items
It is nice to give each child $1 if you are able to do so (we can't this year due to limited funding)
We shopped at the Dollar Tree (a dollar store in Western PA) on the 10% off day. You can work with them to take you in the back of the store and buy by the case. Ideas for Men: flashlights, bungy cords, shaving cream, tool sets, measuring tapes, even ties (they're from their kids - they'll love them more than Brooks Brothers!)
Ideas for Women: Cookware - they have Betty Crocker items - they are awesome, my daughter got me one last year. For a buck, who can complain. They also have some really cute candles, nail kits, eyelash curlers, etc.
Ideas for Teens: nail polish and ear buds
Ideas for Pets: they have cat and dog toys
Grandmas: Eyeglass lanyards - they are really cute and even stylish
Grandpas: see Men
Boys: Here's where I struggled a bit until I found that we could buy Slime, footballs, handballs, and puzzles
Babies: Again, a struggle, but you can find some items, like wash cloths, puppet wash clothes, baby bottles (eh..), and sippy cups and little plates.
We also went to Claire's and bought a ton of 10 for $10 items. You can sometimes get coupons on the web - we got 30% off. Lastly, there is a little local boutique that just moved to town - I asked for discounts - they gave me 40% off. You never know until you ask.
Don't stress out, the kids will be happy with whatever you find. Focus on having fun and decorating to make it magical for them.
I just bought plastic pipe and huge plates to make lollipops and the "north pole" as decorations.....
Good luck!