It is possible! You can have some instability if you have a certain vendor combination and alot of traffic selectors but it should work.
Just include the VLANs or static routes on your MX in the VPN. And then add all the remote VLANs in the little box in the config and it should make child SA's for each traffic selector.
Do keep in mind that any third party peer will need to include ALL of your subnets that participate in VPNs, in their "interesting traffic". You can restrict what they get access to via your site-to-site outbound firewall.
