Native here, born and raised in Tampa area. You have two somewhat different choices. Lakeland is ~ an hour from the West Coast (Tampa) or ~ 2 hrs from the East Coast. Two distinctly different beach settings. Tampa Bay has a number of really nice beaches (Clearwater, Anna Maria, Ft Desoto, Indian Rocks, etc) that are highly ranked in top beaches in US. On the Atlantic side you have beaches like Cocoa, Daytona, etc).
The problem is that if you stay in a beach area on the East coast you are looking at ~ 2hrs to Lakeland. You could stay in Orlando/Kissimmee area and be an hour from Lakeland, but you are going tobe surrounded by tourists and theme parks. I will say there is quite a variety of parks and not all are Disney. You have MGM, Universal, Animal Kingdom, Sea World, etc. There are lots of restaurants and things to do. However, there really isn't much in the way of historic stuff since Orlando basically developed out of Central Florida pastures and orange groves in the 50-60's.
If you stay in Tampa area, you can either stay on the "mainland" in Tampa or stay on the Gulf side in Clearwater/St Petersburg area. A lot depends on your budget. You are coming in the height of tourist season, so lodging prices are higher (this applies to all of FL, not just Tampa) and availability is lower.
In Tampa, you are 30-45 minutes from beaches, depending on which one you go to. There is also a lot more history to Tampa and the surrounding area since it was established in the 1800's. You have a Cuban, Spanish, Italian heritage. There are a lot of places to see. Ybor City is neat, Busch Gardens, Florida Aquarium, Channelside district, are a few that come to mind in the immediate Tampa area. Tarpon Springs and Sponge docks are interesting, Downtown Dunedin are on the Gulf side and worth a visit. If you head north from Tampa about 40 miles on the Suncoast Parkway you can check out some of "old FL" off US19, like Homasassa Springs, Crystal River, Weeki Watchee, etc. There's also a lot of water related things to do, both fresh/salt water fishing, jet skis, dolphin watching cruises, paddle board/kayaking, etc all up and down the coast.
Another option might be to stay South of Tampa Bay in the Bradenton area. Lots of nice beaches like Anna Maria , Ft DeSoto, etc. You will be away from the bigger city feel of Tampa and still only about 1.5 hrs from Lakeland.
The other potential benefit there is that you have some alternate routes to get to Lakeland. From either Tampa or Orlando, the only travel option is Interstate I4. Tons of traffic both East and West and is subject to parking lot/traffic jams almost any time of day. There are a couple alternates like 574 or 92, but these are secondary roads through small towns and still have a lot of traffic.
From Bradenton you could head north on 75 to I4, or you could cut across the FL countryside via 62/37, 301/674/37, etc. Maybe not as quick as the interstate, but not as hectic either.
As far as Lakeland itself, it's typical of any medium size city. Mostly decent area overall, but there are some low income areas that aren't as nice. Not like going into Compton or East LA, but I wouldn't want to stay there. They do have Sherriff Grady Judd, who is somewhat of a celebrity in this area for his hard stance on crime and his always colorful press conferences :)
Feel free to PM for my # if you want to talk or have questions, probably easier than trying to type out everything.
