Can you turn the power way down on these? 100mw is more power than you should be transmitting in a residential neighborhood. You start adding a ground plane antenna and you are asking for a visit from the FCC.
Bigger is not always better. You want folks to be able to pick up the music just beyond where they can see your house, not a half mile away - unless you live out in the country where the average lot size is bigger than 5 acres...
2 mw gives me about a city block, which covers about 10 lots in any direction from my house.