I like using www.hrs.com and found the following hotels which should meet your criteria and which I also know to be decent places. You can check their websites or use hrs and see which one gets you the better deal. I used the dollar feature. I starred the ones I thought were either the most charming or had the best deal & location.
Cristal - $60.45,(by HBF N.exit) includes B.Fast
Hotel Concorde -$90.00 (1 block away from HBF)
InterCity Hotel FF -$94.21 (by HBF N.exit)w/B.Fast
25Hours by Levis - $95.00 (right by the HBF N.exit)
*Intercontinental - $95.00 (on the river, great deal)
Victoria - $96.00 (3 blocks from HBF)w/ B.Fast
*McGallery Savigny - $99.50 (Westend, Nicest neighborhood, a few blocks from HBF)
*Neue Kraeme - $99.50 (great location, near the Hauptwache and Alt Stadt, you can catch your train to airport from here - 15 min.) w/ B.Fast
*Villa Florentina - $105.00 (Westend, includes B.Fast)
*Nizza - $107.00 (gorgeous, central)
Alexander am Zoo - $87.85 w/B.Fast
*Spener House - $109.00 (near Dom & Alt Stadt, quiet, w/B.Fast)
*Art Hotel Robert Meyer - $119.00 (Westend, w/B.fast)
*Dirazi Guesthouse - $125.00 - (Westend)
On the 12th is also the Rose and Tealight festival in the Palmengarten. Might be interesting for you to visit.