I've been to 3 Lia Sophia parties over the summer.
First one was in the afternoon around 1ish, and she had potato salad, macaroni salad, home-made mini-wraps (turkey, ham, cheese), soda, iced tea and cake/coffee.
Second one at 7 pm, and she had mini pizza bagels, chips, vegetable-macaroni salad, soda and cake/coffee.
Third one was at 8, and she went to Costco and bought the shrimp cocktail platter, the mini-hor d'oeuvres platter (franks-in-blankets, potato knishes, spinach rolls, and Jamaican beef patty-type things), a cut fruit platter, and a vegetable dip platter. She also had beer and wine in addition to the usual soft drinks and coffee/tea.
Invite tons of people, because some people won't show up even if they plan on it. Invite people from your kids school, even teachers if you feel friendly enough with them. Tell friends to bring their teenage daughters, grandmothers, anyone, and that whoever brings a friend gets a "surprise". It could be anything, as long as it'll only cost you a few dollars (think 2 for 1 stuff at the dollar store).
Talk about the party a lot before you have it, get people excited about the beautiful jewelry, let them know it's guaranteed for life, if you have any friends who are getting married, suggest she come to the party to take a look at possible brides maids gifts of jewelry. Sound excited to be having the party, make your house "the" place to be on Lia Sophia afternoon. If you have some teen girls to babysit, offer babysitting services while moms attend the party.
Think of people you'd invite to a wedding, and invite those women. Send out lots of invitations, even if you don't know the women well, because the ones who don't get an invitation because you think you don't know them well and they won't want to, they'll STILL say "why didn't I get an invitation" to others. People like to be included, so give invite them even if you think they won't come.
Call people to remind them. I was late to one party because I forgot about it.
Have flashy invitations, in addition to the Lia Sofia ones. GAMES FUN REFRESHMENTS BEAUTIFUL JEWELRY COME SEE
Hand them out at school, scouts, your check-out lady at the supermarket, your school crossing guard, your mailman to give to his wife...trust me, your house won't be overflowing with people, as many won't come, but you've upped your chances of having a good turn-out.
Good luck, and HAVE FUN. I love Lia Sophia jewelry.