Disneyland in December + Vegas

Has anyone done a split Vegas/Disneyland trip? It would just be two adults. I think I have a good idea of what we would do in Vegas (Mob museum, historical walking tour, neon museum, maybe the hop on/hop off bus)…and then go to Disneyland. So maybe two- three days for Vegas and then move to Disneyland

How many days you would suggest for two people at the park(s)? I’m honestly thinking of hiring a Disney planner because we’re not experienced Disney goers and I’m a little nervous about the things I’m reading and peoples’ experiences with lines….i also feel like we’ll be clueless when it comes to the lightning lanes and all the other “get ahead” things they do for rides

We are going in December but haven’t finalized the dates. Preferably, we would go the week before Christmas but would it be better to go two weeks before? I’m just trying to consider crowds, lines, chaos, etc. so the 7-13 or 14-20. Technically, we could also go the 28-3 but I feel like that will still be a heavily condensed week because it’s like Christmas and news years