The Mishna Berura (O.H. 493:1) does permit getting married during the Omer for one who is remarrying a divorcee since it is considered a lesser joy than an initial wedding. It should be noted that it is considered a Mitzvah to remarry one’s divorcee, so long as she had not remarried another man after the initial divorce and that the one is not a Kohen. Nevertheless, Rabbi Itzhak Ben Oualid (Vayomer Itzhak, Likute Dinim, Orah Haim, Dinei HaOmer) writes that even an elderly widow would not be permitted to marry during the Omer, even though it is also not considered especially joyous. He explains that if this were to be permitted, it would create a slippery slope situation in which other cases would be permitted and the original prohibition would be lost.
Regarding attending weddings during the Omer period, Rabbi Shalom Messas (Shemesh Umagen, Orah Haim, § 68) rules leniently if it occurs on a day in which other communities permit weddings. For example, some Ashkenazic communities permit weddings up to and including Rosh Hosdesh Iyar, and thus a Sephardic person would be permitted to attend. Similarly, if one’s custom is to wait until the 34th day to suspend all mourning activities, one would be permitted to attend a wedding on the 33rd day if needed.
Summary: Weddings are generally forbidden during the Omer. One may attend a wedding during this period if it occurs on a day in which other communities permit it.