Congratulations on your upcoming nuptials. :-)
There are a few suggestions for wedding planners in the link below. Are you also asking for suggestions on a beach location? If so, location suggestions might depend on where you're staying?
You might look into the Casa Karma. They do a great job.http://casakarma.net/weddings
Check out Boca De Tomatlan. Nice beach setting for a wedding.
Easy to get to by bus (8 pesos) or taxi from PV about 30 mins.
A few nice hotels there. Esp Villa Armonia Luxury Boutique Hotel. Maybe they can help with wedding plans.
Also some rooms in Mismaloya about 10-15 mons closer to PV but avoid the beach there.
I'm working with Jennifer Lawrence of Beautiful Vallarta Weddings for a wedding next March. We are also a group of 20. She has been great to deal with so far. However, I can't find any review or feedback. I'm just about to give a deposit and feel a bit hesitant.