If you use a linear regulator as was suggested above... You will need a rather large heatsink as the power Wasted is the load current multiplied by the voltage drop across the linear device... Not really a great idea unless your load current's are very low.
.1 A X (24 - 6) is 1.8 watts and 5 Led's can easily draw .1A or 100 mA.
A switching supply (regulator) is a better choice as the loss is the efficiency X the load power IE a 100 mA load @ 6V is .6W and @ 80% efficiency it would be .8(80% Eff) X .6 watts (load ) or .48W (loss) vs 2.4 + .6 (load) or 3 watts loss of energy as heat Vs 1.48 Watts for the linear regulator and 1.8/2.4 = a 25% greater efficiency. I tend to think of switchers as Power converters rather than Voltage converters.
The immediate effect for a very light load @ 100 mA seems a small savings But at higher load currents...
EX:
1A X (24V - 6V) is 18 watts of power lost as heat in the linear device but the switcher will dissipate : (1A X 6V ) X .8 [Eff} or 4.8W and where the linear device will dissipate 24 watts of power and 24 watts/4.8watts is a great deal less wasted energy.. a 5X decrease in wasted power...
However this is Not to say that linears are bad... A Low dropout regulator does a nice job of removing switcher noise with a much smaller footprint than a Pi section filter. It is a good idea to use a small linear behind a switcher at low current for..? Measurements or Audio applications...... There is a Lot of voltage gain in a linear Reg and as long as the I/O differential is just great enough to prevent the device from "Dropping Out" or failing to regulate they can be a useful tool... but when improperly used a real headache