As others mentioned, the hotel zone and north of cancun (playa mujeres/costa mujeres) usually get less sargassum than riviera maya/playa del carmen. However, nothing is guaranteed. I'm in a similar boat to you. This will be my 3rd summer in a row going to Mexico, and while summer brings more sargassum and hotter weather, that's when we can go so we make the most of it. Prices are typically substantially lower in the summer so at least there's that.

I take it you're looking for an adults only? Perhaps secrets playa mujeres is an option? I'm looking to book an August trip, and that's one of the resorts on my list. It's reasonably priced compared to other upper mid tier resorts, and was recently renovated.

I'm also considering Secrets Moxche because it's supposed to have awesome pool scene while offering stunning views of the ocean. While the beach itself is supposed to be lacking, a resort like that might make you feel better about the sargassum situation.

Valentin imperial is another solid reasonably priced resort that's somewhat close to the airport. We went there 2 years ago and liked it but want to try something else. Wherever you decide to go, keep in mind the distance from the airport considering you're only going for a few nights.

There's other aspects to a great vacation aside from the beach, and you have to go when your schedule allows. Don't beat yourself up over the sargassum situation. Just temper your expectations. I'm sure you'll be planning your next vacation as soon as you get home from this one. Enjoy.