Yes, I always thought the first Gate opening at Lenne Square was nothing more than a reaction caused by the pendant (which has special powers might I add) and Lucca's Telepod. The teleporting phase begins and reacts with the Dreamstone within the pendant and opens this Gate out of blind luck. Crono and Marle's actions then effected things. The Entity then saw this as a chance to save the planet, therefore creating the Gate to the ruined future at the best possible moment (when Crono, Lucca and Marle were cornered in the forest). They then arrive in the future, witness the recording of the Day of Lavos, find and repair Robo, go to the End of Time (which was all due to Robo may I add), and the game continues on from there.
Summary: Basically, the first Gate opening was coincidental, the others and the rest of the journey, were altered.
Also, the Entity continued its work through Serege, Schala and Belthasar in Chrono Cross to destroy the Time Devourer (which is a bigger threat then what Lavos ever was).
~LC