I wouldn't use the Cisco to power them.
Cisco PoE switch provides Active PoE (af/at) standard. Active PoE is not compatible with Passive PoE.
PoE af supports two modes, A mode use signal pairs to send power on 100BT devices; mode B use spare pairs on 100BT devices.
Your cisco switch will surely support PoE af A mode (you'll have to check), so even having just 2 pairs, you could power a PoE af capable device in mode A.
However, mikrotik devices support "passive poe" standard, with only a handful SOHO APs additionally supporting af/at, wAP for example (which doesn't have POE Out), so
in theory a single wAP could be powered from the Cisco switch by selecting A mode on the cisco using the layed out cables as they are.
Check
http://wiki.mikrotik.com/index.php?titl ... lity_table as reference for Active Poe switches / RB supporting af/at compatibility (no cisco switches are listed there)
A Better Option
Using the cisco would limit your AP device choice, along with the possibility of daisy chain powering a second one, so a better option would be getting a RB951Ui as first AP, powering it by using a passive POE injector like RBPOE ($5,
http://routerboard.com/RBPOE) at the network closet.
You'll need to crimp a modified ethernet patch cord to use between RBPOE-Patch Pannel, as Passive PoE use pins 4,5 to send DC+, and pins 7,8 for DC- (see
http://wiki.mikrotik.com/wiki/Manual:PoE-In)
Then from the 951Ui, you could power a Hap as AP2.
I wouldn't power anything else from the Hap, as you only have 1 pair to send power; both devices (RB951Ui+Hap) will have a max combined power consumption or 7+4W = 11W which at 24V makes about 500mA; for a single typical CAT5 24AWG wire, this is just the safe current limit.
How far from each other are the 2 conference halls?